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âGiven that the sequence {a_n} is an increasing geometric sequence, and a_1+a_4=9, a_2a_3=8.(1) Find the general formula for the sequence {a_n}; (2) Let S_n be the sum of the first n terms of the sequence {a_n}, and b_n= frac {a_{n+1}}{S_nS_{n+1}}, find the sum of the first n terms of the sequence {b_n}, denoted as T_n.
đĄOkay, so I have this problem about a geometric sequence. Let me try to figure it out step by step. First, part (1) says that {a_n} is an increasing geometric sequence, and we know two things: aâ + aâ = 9 and aâaâ = 8. I need to find the general formula for the sequence.Alright, since it's a geometric sequence, each term is the previous term multiplied by a common ratio, which I'll call q. So, the terms are aâ, aâq, aâq², aâqÂŗ, and so on. Given that it's increasing, that means the common ratio q must be greater than 1 because each term is bigger than the one before it. If q were less than 1, the sequence would be decreasing, which contradicts the given information.Now, let's write down the given equations using the terms of the geometric sequence.First, aâ + aâ = 9. Since aâ is the fourth term, that would be aâ multiplied by qÂŗ. So, the equation becomes:aâ + aâqÂŗ = 9.Second, aâaâ = 8. Let's express aâ and aâ in terms of aâ and q. aâ is aâq and aâ is aâq². Multiplying them together gives:(aâq)(aâq²) = aâ²qÂŗ = 8.So now I have two equations:1. aâ + aâqÂŗ = 92. aâ²qÂŗ = 8Hmm, maybe I can solve these equations simultaneously. Let me see.From equation 2, I can express aâ²qÂŗ = 8, which is the same as (aâqÂŗ) * aâ = 8. Wait, from equation 1, aâ + aâqÂŗ = 9, so aâqÂŗ = 9 - aâ. Let me substitute that into equation 2.So, (9 - aâ) * aâ = 8.Expanding that, I get:9aâ - aâ² = 8.Let me rearrange it:aâ² - 9aâ + 8 = 0.Wait, that's a quadratic equation in terms of aâ. Let me solve it.The quadratic equation is aâ² - 9aâ + 8 = 0. Using the quadratic formula:aâ = [9 Âą sqrt(81 - 32)] / 2= [9 Âą sqrt(49)] / 2= [9 Âą 7] / 2.So, the solutions are:aâ = (9 + 7)/2 = 16/2 = 8,andaâ = (9 - 7)/2 = 2/2 = 1.So, aâ can be 8 or 1. But since the sequence is increasing, which one makes sense?If aâ = 8, then the next term would be 8q, and since the sequence is increasing, q must be greater than 1. Let's check if that works with the other equation.From equation 1: aâ + aâqÂŗ = 9. If aâ = 8, then 8 + 8qÂŗ = 9, which simplifies to 8qÂŗ = 1, so qÂŗ = 1/8, which means q = 1/2. But q = 1/2 is less than 1, which would make the sequence decreasing, not increasing. That contradicts the given information. So, aâ = 8 is not a valid solution.Therefore, aâ must be 1. Let's check that.If aâ = 1, then equation 1 becomes 1 + qÂŗ = 9, so qÂŗ = 8, which means q = 2. That's good because q = 2 is greater than 1, so the sequence is increasing as required.So, the first term is 1, and the common ratio is 2. Therefore, the general formula for the sequence is a_n = aâ * q^{n-1} = 1 * 2^{n-1} = 2^{n-1}.Alright, that seems to make sense. Let me just verify with the given conditions.aâ + aâ = 1 + 2^{3} = 1 + 8 = 9. That's correct.aâaâ = (2^1)(2^2) = 2 * 4 = 8. That's also correct.Great, so part (1) is solved. The general formula is a_n = 2^{n-1}.Now, moving on to part (2). It says that S_n is the sum of the first n terms of the sequence {a_n}, and b_n = a_{n+1}/(S_n S_{n+1}). I need to find the sum of the first n terms of the sequence {b_n}, denoted as T_n.First, let's recall that the sum of the first n terms of a geometric sequence is given by S_n = aâ(1 - q^n)/(1 - q). Since aâ = 1 and q = 2, plugging in those values:S_n = (1 - 2^n)/(1 - 2) = (1 - 2^n)/(-1) = (2^n - 1).So, S_n = 2^n - 1.Similarly, S_{n+1} = 2^{n+1} - 1.Now, let's write down b_n:b_n = a_{n+1}/(S_n S_{n+1}).We know that a_{n+1} = 2^{n} because a_n = 2^{n-1}, so a_{n+1} = 2^{(n+1)-1} = 2^n.Therefore, b_n = 2^n / [(2^n - 1)(2^{n+1} - 1)].Hmm, that looks a bit complicated. Maybe I can simplify this expression.Let me see if I can express b_n as a difference of two fractions. That is, maybe b_n can be written as something like 1/(2^n - 1) - 1/(2^{n+1} - 1). Let me check.Let me compute 1/(2^n - 1) - 1/(2^{n+1} - 1):= [ (2^{n+1} - 1) - (2^n - 1) ] / [(2^n - 1)(2^{n+1} - 1)]= [2^{n+1} - 1 - 2^n + 1] / [(2^n - 1)(2^{n+1} - 1)]= [2^{n+1} - 2^n] / [(2^n - 1)(2^{n+1} - 1)]= [2^n(2 - 1)] / [(2^n - 1)(2^{n+1} - 1)]= [2^n(1)] / [(2^n - 1)(2^{n+1} - 1)]= 2^n / [(2^n - 1)(2^{n+1} - 1)].Hey, that's exactly equal to b_n! So, b_n = 1/(2^n - 1) - 1/(2^{n+1} - 1).Wow, that's a telescoping series! That should make finding T_n much easier.So, T_n is the sum from k = 1 to n of b_k.Expressed as:T_n = ÎŖ_{k=1}^n [1/(2^k - 1) - 1/(2^{k+1} - 1)].Let me write out the terms to see the cancellation:When k = 1: 1/(2^1 - 1) - 1/(2^2 - 1) = 1/1 - 1/3When k = 2: 1/(2^2 - 1) - 1/(2^3 - 1) = 1/3 - 1/7When k = 3: 1/(2^3 - 1) - 1/(2^4 - 1) = 1/7 - 1/15...When k = n: 1/(2^n - 1) - 1/(2^{n+1} - 1)So, when we add all these up, most of the intermediate terms cancel out:T_n = (1/1 - 1/3) + (1/3 - 1/7) + (1/7 - 1/15) + ... + (1/(2^n - 1) - 1/(2^{n+1} - 1)).All the -1/3 cancels with +1/3, -1/7 cancels with +1/7, and so on, up until -1/(2^n - 1) cancels with +1/(2^n - 1). So, what's left is the first term of the first expression and the last term of the last expression:T_n = 1/1 - 1/(2^{n+1} - 1).Simplifying, that's:T_n = 1 - 1/(2^{n+1} - 1).So, that's the sum of the first n terms of the sequence {b_n}.Let me just verify this with a small n to make sure it's correct.Let's take n = 1.Compute T_1 = b_1.Compute b_1 = a_2/(S_1 S_2).a_2 = 2^{2-1} = 2^1 = 2.S_1 = 2^1 - 1 = 1.S_2 = 2^2 - 1 = 3.So, b_1 = 2/(1*3) = 2/3.From the formula, T_1 = 1 - 1/(2^{2} - 1) = 1 - 1/3 = 2/3. That matches.Now, n = 2.Compute T_2 = b_1 + b_2.Compute b_2 = a_3/(S_2 S_3).a_3 = 2^{3-1} = 4.S_2 = 3.S_3 = 2^3 - 1 = 7.So, b_2 = 4/(3*7) = 4/21.Thus, T_2 = 2/3 + 4/21 = (14/21 + 4/21) = 18/21 = 6/7.From the formula, T_2 = 1 - 1/(2^{3} - 1) = 1 - 1/7 = 6/7. That also matches.Good, so the formula seems to work for n = 1 and n = 2.Therefore, I'm confident that the sum T_n is 1 - 1/(2^{n+1} - 1).**Final Answer**(1) The general formula for the sequence is boxed{a_n = 2^{n-1}}.(2) The sum of the first n terms of the sequence {b_n} is boxed{1 - frac{1}{2^{n+1} - 1}}.
âGiven a set of data {x_1,x_2,x_3,x_4,x_5} with a mean of bar{x}=2 and variance of frac{1}{3}, find the mean and variance of another set of data {3x_1-2,3x_2-2,3x_3-2,3x_4-2,3x_5-2} ( Â Â ).A: 2, frac{1}{3}B: 2, 1C: 4, frac{1}{3}D: 4, 3
đĄFirst, I need to determine the new mean of the transformed data set. The original mean is 2. When each data point is multiplied by 3 and then reduced by 2, the mean will also undergo the same transformation. So, the new mean will be 3 times the original mean minus 2.Next, I need to calculate the new variance. The original variance is 1/3. When each data point is multiplied by a constant (in this case, 3), the variance is multiplied by the square of that constant. Therefore, the new variance will be 3 squared times the original variance.By applying these transformations, I can find the new mean and variance for the modified data set.
âBridget bought a bag of apples at the grocery store. She gave one-third of the apples to Ann. Then she gave Cassie 5 apples and gave Dan 2 apples, keeping 7 apples for herself. How many apples did Bridget buy?textbf{(A)} 18 qquadtextbf{(B)} 21 qquadtextbf{(C)} 24 qquadtextbf{(D)} 27 qquadtextbf{(E)} 30
đĄLet ( x ) be the total number of apples Bridget bought.1. Bridget gave one-third of the apples to Ann: [ frac{x}{3} ] This leaves Bridget with: [ x - frac{x}{3} = frac{2x}{3} ]2. Bridget then gave Cassie 5 apples and Dan 2 apples, which is a total of: [ 5 + 2 = 7 text{ apples} ] After giving these apples, the number of apples Bridget had left is: [ frac{2x}{3} - 7 ]3. Bridget kept 7 apples for herself. Therefore, we set up the equation: [ frac{2x}{3} - 7 = 7 ]4. Solving for ( x ): - Add 7 to both sides: [ frac{2x}{3} = 14 ] - Multiply both sides by ( frac{3}{2} ): [ x = 21 ]Thus, Bridget originally bought 21 apples.
âThe graph of y = f(x) is shown above in the initial problem. Which is the graph of y = fleft(frac{2 - x}{3}right)?[asy]unitsize(0.3 cm);picture[] graf;int i, n;real func(real x) { real y; if (x >= -3 && x <= 0) {y = -2 - x;} if (x >= 0 && x <= 2) {y = sqrt(4 - (x - 2)^2) - 2;} if (x >= 2 && x <= 3) {y = 2*(x - 2);} return(y);}real funcb(real x) { return(func((2 - x)/3));}for (n = 1; n <= 5; ++n) { graf[n] = new picture; for (i = -8; i <= 8; ++i) { draw(graf[n],(i,-8)--(i,8),gray(0.7)); draw(graf[n],(-8,i)--(8,i),gray(0.7)); } draw(graf[n],(-8,0)--(8,0),Arrows(6)); draw(graf[n],(0,-8)--(0,8),Arrows(6)); label(graf[n],"x", (8,0), E); label(graf[n],"y", (0,8), N);}// Create variationsdraw(graf[1],shift((2/3,0))*xscale(1/3)*reflect((0,0),(0,1))*graph(func,-3,3),red);draw(graf[2],graph(funcb,-5,7),red);draw(graf[3],shift((2,0))*xscale(1/3)*reflect((0,0),(0,1))*graph(func,-3,3),red);draw(graf[4],shift((2/3,0))*xscale(3)*reflect((0,0),(0,1))*graph(func,-3,3),red);draw(graf[5],shift((2/3,0))*xscale(1/3)*reflect((0,0),(0,1))*graph(func,-3,3),red);label(graf[1], "A", (0,-10));label(graf[2], "B", (0,-10));label(graf[3], "C", (0,-10));label(graf[4], "D", (0,-10));label(graf[5], "E", (0,-10));add(graf[1]);add(shift((20,0))*(graf[2]));add(shift((40,0))*(graf[3]));add(shift((10,-20))*(graf[4]));add(shift((30,-20))*(graf[5]));[/asy]
đĄOkay, so I have this problem where I need to figure out which graph corresponds to the transformation ( y = fleft(frac{2 - x}{3}right) ). The original graph of ( y = f(x) ) is given, but since it's an image, I can't see it directly. However, the Asymptote code describes the function ( f(x) ) in three parts:1. For ( x ) between -3 and 0, ( f(x) = -2 - x ). That sounds like a linear function with a negative slope.2. For ( x ) between 0 and 2, ( f(x) = sqrt{4 - (x - 2)^2} - 2 ). Hmm, that looks like the equation of a semicircle. Let me see: ( sqrt{4 - (x - 2)^2} ) is the upper half of a circle with radius 2 centered at (2, 0), and then subtracting 2 would shift it down by 2 units. So, it's a semicircle sitting below the x-axis.3. For ( x ) between 2 and 3, ( f(x) = 2(x - 2) ). That's another linear function with a positive slope, starting at (2, 0) and going up to (3, 2).So, putting that together, the original graph has three parts: a line from (-3, -5) to (0, -2), a semicircle from (0, -2) to (2, 0), and then another line from (2, 0) to (3, 2). Got it.Now, I need to figure out how the transformation ( y = fleft(frac{2 - x}{3}right) ) affects this graph. Let me break down the transformation step by step.First, let's rewrite the transformation inside the function:( frac{2 - x}{3} )I can think of this as a combination of transformations. Let's see:1. Start with ( x ).2. Replace ( x ) with ( -x ) to get ( -x ). This reflects the graph over the y-axis.3. Then, replace ( x ) with ( x - 2 ) to get ( -(x - 2) = -x + 2 ). Wait, actually, that's not quite right. Let me think again.Actually, the expression ( frac{2 - x}{3} ) can be rewritten as ( frac{2}{3} - frac{x}{3} ). So, this is a horizontal scaling and a horizontal shift.Breaking it down:- The ( -x ) inside the function indicates a reflection over the y-axis.- The ( frac{x}{3} ) indicates a horizontal stretch by a factor of 3. But since it's combined with the reflection, it's actually a horizontal compression by a factor of 3 if we consider the reflection first.- The ( frac{2}{3} ) term is a horizontal shift. Since it's added inside the function argument, it shifts the graph to the right by ( frac{2}{3} ) units.Wait, let me verify that. When dealing with function transformations, the general form is ( f(bx + c) ). The transformations are:- Horizontal scaling by ( frac{1}{|b|} ). If ( b > 1 ), it's a compression; if ( 0 < b < 1 ), it's a stretch.- Horizontal shift by ( -frac{c}{b} ). The sign is important here.In our case, ( fleft(frac{2 - x}{3}right) ) can be rewritten as ( fleft(-frac{1}{3}x + frac{2}{3}right) ). So, ( b = -frac{1}{3} ) and ( c = frac{2}{3} ).Therefore:- The horizontal scaling factor is ( frac{1}{|b|} = 3 ). Since ( b ) is negative, it also includes a reflection over the y-axis.- The horizontal shift is ( -frac{c}{b} = -frac{frac{2}{3}}{-frac{1}{3}} = 2 ). Wait, that's a shift of 2 units to the right.But hold on, in the expression ( fleft(-frac{1}{3}x + frac{2}{3}right) ), the shift is actually ( frac{2}{3} ) units, not 2. Let me double-check.The general form is ( f(b(x - h)) ), where ( h ) is the horizontal shift. So, let's factor out the ( b ):( fleft(-frac{1}{3}x + frac{2}{3}right) = fleft(-frac{1}{3}(x - 2)right) ).So, ( h = 2 ). Therefore, the horizontal shift is 2 units to the right, but because of the reflection and scaling, it's a bit tricky.Wait, no. Let's be precise. The transformation is ( fleft(frac{2 - x}{3}right) ). Let me consider substituting ( u = frac{2 - x}{3} ). Then, ( x = 2 - 3u ). So, for each point ( (u, y) ) on the original graph, the transformed graph has the point ( (2 - 3u, y) ).This means that:- The graph is reflected over the y-axis because of the negative sign.- It's horizontally stretched by a factor of 3 because of the 3 in the denominator.- It's shifted to the right by 2 units because of the +2.Wait, that seems conflicting with my earlier conclusion. Let me think again.If ( u = frac{2 - x}{3} ), then solving for ( x ) gives ( x = 2 - 3u ). So, for each point ( (u, y) ) on ( f(u) ), the corresponding point on the transformed graph is ( (2 - 3u, y) ).So, to get from ( u ) to ( x ), we first scale ( u ) by 3 (which is a horizontal stretch by 3), then reflect over the y-axis (because of the negative sign), and then shift right by 2 units.But in terms of transformations applied to the graph, the order is important. When you have ( f(b(x - h)) ), the shift happens after the scaling and reflection.So, in this case, the transformation is a horizontal reflection, followed by a horizontal stretch by 3, and then a horizontal shift to the right by 2 units.But wait, actually, the order is a bit different. Let's consider the transformation as replacing ( x ) with ( frac{2 - x}{3} ). So, starting from ( x ), we first subtract 2, then divide by 3, but with a negative sign.Alternatively, it's equivalent to reflecting over the y-axis, then scaling by 3, and then shifting.But I think the correct order is:1. Start with ( f(x) ).2. Reflect over the y-axis: ( f(-x) ).3. Then, replace ( x ) with ( frac{x}{3} ): ( f(-frac{x}{3}) ). This is a horizontal stretch by 3.4. Then, replace ( x ) with ( x - 2 ): ( f(-frac{(x - 2)}{3}) = f(frac{2 - x}{3}) ). This is a horizontal shift to the right by 2 units.Wait, but actually, when you have ( f(-frac{x}{3}) ), it's a horizontal reflection and a horizontal stretch. Then, shifting right by 2 would be replacing ( x ) with ( x - 2 ), so ( f(-frac{(x - 2)}{3}) ).But in terms of the graph, the order of transformations is:- First, reflect over the y-axis.- Then, stretch horizontally by 3.- Then, shift right by 2 units.But let me confirm this with an example. Suppose we have a point (a, b) on the original graph ( f(x) ). Then, on the transformed graph ( fleft(frac{2 - x}{3}right) ), the point would be at ( x = 2 - 3a ), because:( frac{2 - x}{3} = a ) implies ( x = 2 - 3a ).So, the original point (a, b) is transformed to (2 - 3a, b).This means:- The x-coordinate is scaled by -3 (which is a reflection and a stretch) and then shifted by +2.So, the transformation is a horizontal reflection, followed by a horizontal stretch by 3, and then a horizontal shift to the right by 2 units.But wait, in terms of the graph, the reflection and stretch are combined, and then the shift is applied after.So, to visualize this, I need to take the original graph, flip it over the y-axis, stretch it horizontally by a factor of 3, and then move it 2 units to the right.Let me think about how each part of the original graph will transform.1. The linear part from (-3, -5) to (0, -2):After reflection over y-axis, this part becomes from (3, -5) to (0, -2). Then, stretching horizontally by 3, the point (3, -5) becomes (9, -5), and (0, -2) remains (0, -2). Then, shifting right by 2 units, (9, -5) becomes (11, -5), and (0, -2) becomes (2, -2). So, this linear part would go from (2, -2) to (11, -5). Wait, that seems like a steep negative slope.But wait, actually, the reflection over y-axis would flip the x-coordinates. So, the original segment from (-3, -5) to (0, -2) becomes from (3, -5) to (0, -2). Then, stretching horizontally by 3 would take (3, -5) to (9, -5) and (0, -2) to (0, -2). Then, shifting right by 2 would move (9, -5) to (11, -5) and (0, -2) to (2, -2). So, the transformed linear part is from (2, -2) to (11, -5). That seems correct.2. The semicircle part from (0, -2) to (2, 0):After reflection over y-axis, this semicircle would be mirrored to the right side, so from (0, -2) to (-2, 0). Wait, no. Reflecting over y-axis would flip the x-coordinates, so the semicircle from (0, -2) to (2, 0) becomes from (0, -2) to (-2, 0). Then, stretching horizontally by 3 would take (0, -2) to (0, -2) and (-2, 0) to (-6, 0). Then, shifting right by 2 would move (0, -2) to (2, -2) and (-6, 0) to (-4, 0). So, the semicircle is now from (2, -2) to (-4, 0). Wait, that doesn't make sense because stretching and shifting would change the center.Wait, maybe I need to think about the equation of the semicircle after transformation.The original semicircle is ( y = sqrt{4 - (x - 2)^2} - 2 ) for ( x ) between 0 and 2. After the transformation ( x to frac{2 - x}{3} ), let's substitute:Let ( u = frac{2 - x}{3} ). Then, ( x = 2 - 3u ).So, the equation becomes:( y = sqrt{4 - ( (2 - 3u) - 2 )^2 } - 2 = sqrt{4 - (-3u)^2 } - 2 = sqrt{4 - 9u^2} - 2 ).But since ( u = frac{2 - x}{3} ), we can write:( y = sqrt{4 - 9left(frac{2 - x}{3}right)^2} - 2 = sqrt{4 - (2 - x)^2} - 2 ).Wait, that simplifies to ( y = sqrt{4 - (2 - x)^2} - 2 ). Let me expand ( (2 - x)^2 ):( (2 - x)^2 = x^2 - 4x + 4 ).So, ( y = sqrt{4 - x^2 + 4x - 4} - 2 = sqrt{4x - x^2} - 2 ).Hmm, that's ( y = sqrt{-x^2 + 4x} - 2 ). Let me write it as ( y = sqrt{-(x^2 - 4x)} - 2 ). Completing the square inside the square root:( x^2 - 4x = (x - 2)^2 - 4 ).So, ( y = sqrt{ -[(x - 2)^2 - 4] } - 2 = sqrt{4 - (x - 2)^2} - 2 ).Wait, that's interesting. So, after transformation, the semicircle equation becomes ( y = sqrt{4 - (x - 2)^2} - 2 ). That's the same as the original semicircle but centered at (2, -2) instead of (2, 0). Wait, no, the original semicircle was centered at (2, 0) but shifted down by 2, so it's centered at (2, -2). But after transformation, it's still centered at (2, -2). So, the semicircle remains the same? That can't be right.Wait, no. Let me see. The original semicircle was from (0, -2) to (2, 0). After transformation, the equation is ( y = sqrt{4 - (x - 2)^2} - 2 ), which is a semicircle centered at (2, -2) with radius 2. So, it spans from (0, -2) to (4, -2), but only the upper half. Wait, no, the square root function gives the upper half, so it's from (0, -2) to (4, -2), but the y-values go from -2 up to 0. So, the semicircle is now from (0, -2) to (4, -2), peaking at (2, 0). Wait, that seems different from the original.But hold on, the original semicircle was from (0, -2) to (2, 0), but after transformation, it's from (0, -2) to (4, -2), peaking at (2, 0). So, it's wider and shifted to the right.Wait, but in the transformed function, the semicircle is centered at (2, -2) with radius 2, so it goes from (0, -2) to (4, -2), with the top at (2, 0). So, that's a different shape than the original.3. The linear part from (2, 0) to (3, 2):After reflection over y-axis, this becomes from (-2, 0) to (-3, 2). Then, stretching horizontally by 3, (-2, 0) becomes (-6, 0) and (-3, 2) becomes (-9, 2). Then, shifting right by 2 units, (-6, 0) becomes (-4, 0) and (-9, 2) becomes (-7, 2). So, the transformed linear part is from (-4, 0) to (-7, 2). Wait, that seems like a line with a negative slope.But wait, the original linear part was from (2, 0) to (3, 2), which is a positive slope. After reflection, it's from (-2, 0) to (-3, 2), which is a negative slope. Then, stretching and shifting would preserve the slope direction but change the steepness.Wait, actually, the slope of the original line is ( (2 - 0)/(3 - 2) = 2 ). After reflection, the slope becomes ( (2 - 0)/(-3 - (-2)) = 2/(-1) = -2 ). Then, stretching horizontally by 3 would affect the slope. The slope formula is rise over run. If we stretch horizontally by 3, the run becomes 3 times longer, so the slope becomes ( -2 / 3 ). Then, shifting right by 2 units doesn't affect the slope.So, the transformed linear part has a slope of ( -2/3 ). Starting from (-4, 0), going to (-7, 2). Wait, let me calculate the slope between (-4, 0) and (-7, 2):Slope = ( (2 - 0)/(-7 - (-4)) = 2/(-3) = -2/3 ). Yes, that matches.So, putting it all together, the transformed graph has:1. A linear part from (2, -2) to (11, -5) with a slope of ( (-5 - (-2))/(11 - 2) = (-3)/9 = -1/3 ). Wait, that doesn't match my earlier conclusion. Wait, no, the slope was supposed to be -1/3? Wait, no, the original slope was -1 from (-3, -5) to (0, -2). After reflection, it became a positive slope, but then stretched and shifted.Wait, I'm getting confused. Let me try to list the transformed points:Original points:1. (-3, -5) becomes (2 - 3*(-3), -5) = (2 + 9, -5) = (11, -5)2. (0, -2) becomes (2 - 3*0, -2) = (2, -2)3. (2, 0) becomes (2 - 3*2, 0) = (2 - 6, 0) = (-4, 0)4. (3, 2) becomes (2 - 3*3, 2) = (2 - 9, 2) = (-7, 2)So, the transformed graph has key points at (11, -5), (2, -2), (-4, 0), and (-7, 2).Wait, but the original graph had three parts:1. From (-3, -5) to (0, -2): transformed to from (11, -5) to (2, -2)2. From (0, -2) to (2, 0): transformed to from (2, -2) to (-4, 0)3. From (2, 0) to (3, 2): transformed to from (-4, 0) to (-7, 2)So, the transformed graph has three parts:1. A line from (11, -5) to (2, -2)2. A semicircle from (2, -2) to (-4, 0)3. A line from (-4, 0) to (-7, 2)Wait, but the semicircle part is now from (2, -2) to (-4, 0), which is a semicircle centered at (2 - 3*2, -2) = (2 - 6, -2) = (-4, -2)? Wait, no, earlier I derived that the semicircle equation becomes ( y = sqrt{4 - (x - 2)^2} - 2 ), which is centered at (2, -2). So, it spans from (0, -2) to (4, -2), but since we transformed the original semicircle from (0, -2) to (2, 0), after transformation, it's from (2, -2) to (-4, 0). Wait, that doesn't make sense because the center is at (2, -2), so it should span from (0, -2) to (4, -2), but the transformed points are (2, -2) to (-4, 0). Hmm, maybe I made a mistake in the transformation of the semicircle.Wait, let's go back. The original semicircle is from (0, -2) to (2, 0). After transformation, the points (0, -2) become (2, -2) and (2, 0) become (-4, 0). So, the semicircle is now from (2, -2) to (-4, 0). But the equation we derived is ( y = sqrt{4 - (x - 2)^2} - 2 ), which is a semicircle centered at (2, -2) with radius 2. So, it should span from (0, -2) to (4, -2), but our transformed points are (2, -2) to (-4, 0). That seems inconsistent.Wait, maybe I need to consider the domain of the transformed function. The original semicircle was for ( x ) between 0 and 2. After transformation, ( u = frac{2 - x}{3} ), so ( u ) is between ( frac{2 - 0}{3} = frac{2}{3} ) and ( frac{2 - 2}{3} = 0 ). So, ( u ) goes from ( frac{2}{3} ) to 0, which corresponds to ( x ) going from ( 2 - 3*(2/3) = 2 - 2 = 0 ) to ( 2 - 3*0 = 2 ). Wait, that's the same as the original domain. Hmm, I'm getting confused.Maybe I should plot the transformed points:- (11, -5): from (-3, -5)- (2, -2): from (0, -2)- (-4, 0): from (2, 0)- (-7, 2): from (3, 2)So, the transformed graph has:1. A line from (11, -5) to (2, -2)2. A semicircle from (2, -2) to (-4, 0)3. A line from (-4, 0) to (-7, 2)Wait, but the semicircle from (2, -2) to (-4, 0) would have a center somewhere. Let me find the center. The midpoint between (2, -2) and (-4, 0) is ( left(frac{2 + (-4)}{2}, frac{-2 + 0}{2}right) = (-1, -1) ). The radius would be the distance from (-1, -1) to (2, -2):Distance = ( sqrt{(2 - (-1))^2 + (-2 - (-1))^2} = sqrt{3^2 + (-1)^2} = sqrt{9 + 1} = sqrt{10} ).But the equation we derived earlier was ( y = sqrt{4 - (x - 2)^2} - 2 ), which is a semicircle with radius 2 centered at (2, -2). So, it's inconsistent with the transformed points.I think I made a mistake in interpreting the transformation of the semicircle. Let me try again.The original semicircle is ( y = sqrt{4 - (x - 2)^2} - 2 ) for ( x ) between 0 and 2. After the transformation ( x to frac{2 - x}{3} ), let's substitute ( u = frac{2 - x}{3} ), so ( x = 2 - 3u ).Substituting into the original equation:( y = sqrt{4 - ( (2 - 3u) - 2 )^2 } - 2 = sqrt{4 - (-3u)^2} - 2 = sqrt{4 - 9u^2} - 2 ).But ( u = frac{2 - x}{3} ), so we can write:( y = sqrt{4 - 9left(frac{2 - x}{3}right)^2} - 2 = sqrt{4 - (2 - x)^2} - 2 ).Wait, that's the same as before. So, the transformed semicircle is ( y = sqrt{4 - (2 - x)^2} - 2 ). Let me rewrite this:( y = sqrt{4 - (2 - x)^2} - 2 ).Let me expand ( (2 - x)^2 ):( (2 - x)^2 = x^2 - 4x + 4 ).So, ( y = sqrt{4 - x^2 + 4x - 4} - 2 = sqrt{4x - x^2} - 2 ).This can be rewritten as:( y = sqrt{-(x^2 - 4x)} - 2 = sqrt{-(x^2 - 4x + 4 - 4)} - 2 = sqrt{-(x - 2)^2 + 4} - 2 ).So, ( y = sqrt{4 - (x - 2)^2} - 2 ).Wait, that's the same as the original semicircle equation. So, the semicircle remains the same? That can't be right because the transformation should change it.Wait, no. The original semicircle was ( y = sqrt{4 - (x - 2)^2} - 2 ) for ( x ) between 0 and 2. After transformation, it's the same equation but for different ( x ) values. Specifically, the domain of ( u ) was ( 0 leq u leq 2 ), which translates to ( x ) values from ( 2 - 3*2 = -4 ) to ( 2 - 3*0 = 2 ). So, the transformed semicircle is ( y = sqrt{4 - (x - 2)^2} - 2 ) for ( x ) between -4 and 2.So, the semicircle is now centered at (2, -2) with radius 2, spanning from (-4, -2) to (4, -2), but only the upper half. Wait, no, the square root function gives the upper half, so it's from (0, -2) to (4, -2), but that's not matching the transformed points.Wait, I'm getting tangled up. Let me try to plot the transformed points:- The semicircle part is from (2, -2) to (-4, 0). So, it's a semicircle that starts at (2, -2), goes up to (-4, 0), and back down? Wait, no, because it's a function, it can't go back down. So, it must be a semicircle that is either the upper or lower half.Given the equation ( y = sqrt{4 - (x - 2)^2} - 2 ), this is the upper half of the circle centered at (2, -2) with radius 2. So, it spans from ( x = 0 ) to ( x = 4 ), with ( y ) ranging from -2 to 0. But our transformed points are (2, -2) and (-4, 0). So, how does that fit?Wait, if the semicircle is from (0, -2) to (4, -2), peaking at (2, 0), then the transformed points (2, -2) and (-4, 0) don't lie on this semicircle. Because (2, -2) is the center, and (-4, 0) is outside the radius.Hmm, I think I'm making a mistake in the transformation. Let me try a different approach.Instead of trying to transform each point, maybe I should consider the effect of the transformation on the entire graph.The transformation is ( y = fleft(frac{2 - x}{3}right) ). Let's break it down:1. Start with ( f(x) ).2. Replace ( x ) with ( -x ): this reflects the graph over the y-axis.3. Replace ( x ) with ( frac{x}{3} ): this horizontally stretches the graph by a factor of 3.4. Replace ( x ) with ( x - 2 ): this shifts the graph 2 units to the right.Wait, but the order of transformations matters. When you have multiple transformations inside the function argument, you apply them in the reverse order. So, to get ( fleft(frac{2 - x}{3}right) ), you first reflect over y-axis, then stretch by 3, then shift right by 2.But let me think about it step by step:- Original graph: ( f(x) ).- After reflecting over y-axis: ( f(-x) ).- After stretching horizontally by 3: ( f(-x/3) ).- After shifting right by 2: ( f(-(x - 2)/3) = fleft(frac{2 - x}{3}right) ).Yes, that's correct. So, the order is reflect, then stretch, then shift.So, to visualize:1. Reflect the original graph over the y-axis. This flips the graph horizontally.2. Stretch the reflected graph horizontally by a factor of 3. This makes the graph wider.3. Shift the stretched graph 2 units to the right.So, let's apply this to each part of the original graph.1. The linear part from (-3, -5) to (0, -2):- Reflect over y-axis: becomes from (3, -5) to (0, -2).- Stretch horizontally by 3: becomes from (9, -5) to (0, -2).- Shift right by 2: becomes from (11, -5) to (2, -2).So, this part becomes a line from (11, -5) to (2, -2).2. The semicircle from (0, -2) to (2, 0):- Reflect over y-axis: becomes from (0, -2) to (-2, 0).- Stretch horizontally by 3: becomes from (0, -2) to (-6, 0).- Shift right by 2: becomes from (2, -2) to (-4, 0).So, this part becomes a semicircle from (2, -2) to (-4, 0).3. The linear part from (2, 0) to (3, 2):- Reflect over y-axis: becomes from (-2, 0) to (-3, 2).- Stretch horizontally by 3: becomes from (-6, 0) to (-9, 2).- Shift right by 2: becomes from (-4, 0) to (-7, 2).So, this part becomes a line from (-4, 0) to (-7, 2).Putting it all together, the transformed graph has:1. A line from (11, -5) to (2, -2).2. A semicircle from (2, -2) to (-4, 0).3. A line from (-4, 0) to (-7, 2).Now, looking at the Asymptote code, the options are labeled A to E. The code draws each graph with different transformations:- graf[1]: shift((2/3,0)) * xscale(1/3) * reflect((0,0),(0,1)) * graph(func,-3,3)- graf[2]: graph(funcb,-5,7)- graf[3]: shift((2,0)) * xscale(1/3) * reflect((0,0),(0,1)) * graph(func,-3,3)- graf[4]: shift((2/3,0)) * xscale(3) * reflect((0,0),(0,1)) * graph(func,-3,3)- graf[5]: same as graf[1]So, graf[2] is the direct graph of funcb, which is ( fleft(frac{2 - x}{3}right) ). The others are different transformations.But in the Asymptote code, graf[2] is drawn as graph(funcb,-5,7), which is the correct transformation. The other graf[1], graf[3], graf[4], graf[5] are different transformations.But in the initial problem, the user says that graf[2] is labeled as B, and graf[1] is labeled as A, etc.So, according to the Asymptote code, graf[2] is the correct graph, which is option B.But wait, in my earlier analysis, the transformed graph has points at (11, -5), (2, -2), (-4, 0), (-7, 2). Looking at the Asymptote code, graf[2] is drawn from -5 to 7 on the x-axis, which would include all these points.Whereas graf[1] is shifted by (2/3, 0) and scaled by 1/3, which would compress the graph horizontally and shift it a little, but not as much as graf[2].Similarly, graf[3] is shifted by (2,0) and scaled by 1/3, which would be a different transformation.graf[4] is shifted by (2/3,0) and scaled by 3, which is a horizontal stretch, but not the same as graf[2].graf[5] is same as graf[1].Therefore, graf[2] is the correct transformation, which is option B.So, the answer should be B.
âAlice, Bob, and Conway are playing rock-paper-scissors. Each player plays against each of the other 2 players and each pair plays until a winner is decided (i.e. in the event of a tie, they play again). What is the probability that each player wins exactly once?
đĄOkay, so I have this problem where Alice, Bob, and Conway are playing rock-paper-scissors. Each of them plays against the other two, and they keep playing until there's a winner in each match. The question is asking for the probability that each player wins exactly once. Hmm, let me try to figure this out step by step.First, I need to understand the structure of the game. There are three players, and each pair plays until one wins. So, there are three matches in total: Alice vs. Bob, Bob vs. Conway, and Conway vs. Alice. Each match is independent, and in each match, there are two possible outcomes: one player wins, or the other wins. Since they keep playing until there's a winner, ties don't count, so each match will eventually result in a win for one of the two players.Now, the problem is asking for the probability that each player wins exactly once. That means, out of the three matches, each player should have one win and one loss. Wait, actually, each player plays two matches, right? Because each player plays against the other two. So, each player has two matches, and we want each player to win exactly once. That means, in total, each player has one win and one loss across their two matches.Let me think about how this can happen. Since there are three players, and each has two matches, the total number of wins across all players is three (since each match has one win). So, if each player wins exactly once, that adds up perfectly because 3 players each winning once gives us three total wins.Now, I need to figure out how many possible outcomes there are in total and how many of those outcomes satisfy the condition that each player wins exactly once.First, let's calculate the total number of possible outcomes. Each match has two possible outcomes (either player A wins or player B wins). Since there are three matches, the total number of possible outcomes is 2^3 = 8. So, there are 8 possible ways the matches can go.Now, out of these 8 possible outcomes, how many of them result in each player winning exactly once? Let's try to list them out.Let's denote the matches as follows:1. Alice vs. Bob2. Bob vs. Conway3. Conway vs. AliceWe can represent each outcome as a combination of who wins each match. For example, one possible outcome is Alice beats Bob, Bob beats Conway, and Conway beats Alice. Let's see if this satisfies the condition that each player wins exactly once.- Alice wins against Bob.- Bob wins against Conway.- Conway wins against Alice.So, in this case:- Alice has one win (against Bob) and one loss (against Conway).- Bob has one win (against Conway) and one loss (against Alice).- Conway has one win (against Alice) and one loss (against Bob).Yes, this satisfies the condition. So, this is one favorable outcome.Is there another outcome where each player wins exactly once? Let's see.Another possible outcome is:- Alice loses to Bob.- Bob loses to Conway.- Conway loses to Alice.So, in this case:- Alice has one win (against Conway) and one loss (against Bob).- Bob has one win (against Alice) and one loss (against Conway).- Conway has one win (against Bob) and one loss (against Alice).Yes, this also satisfies the condition. So, this is another favorable outcome.Are there any more? Let's see.If we consider other outcomes, for example:- Alice beats Bob, Alice beats Conway, and Bob beats Conway.In this case:- Alice has two wins (against Bob and Conway).- Bob has one win (against Conway) and one loss (against Alice).- Conway has two losses.This doesn't satisfy the condition because Alice has two wins, and Conway has two losses.Another outcome:- Alice beats Bob, Conway beats Bob, and Conway beats Alice.In this case:- Alice has one win (against Bob) and one loss (against Conway).- Bob has two losses (against Alice and Conway).- Conway has one win (against Bob) and one win (against Alice).Wait, no, Conway has two wins here, which is not allowed because we need each player to have exactly one win.So, this outcome doesn't satisfy the condition either.Similarly, if we consider:- Bob beats Alice, Bob beats Conway, and Conway beats Alice.Here:- Bob has two wins (against Alice and Conway).- Alice has two losses (against Bob and Conway).- Conway has one win (against Alice).Again, Bob has two wins, so this doesn't satisfy the condition.Another outcome:- Alice beats Bob, Conway beats Bob, and Alice beats Conway.In this case:- Alice has two wins (against Bob and Conway).- Bob has two losses (against Alice and Conway).- Conway has one win (against Bob).Again, Alice has two wins, so this doesn't work.Wait, so far, I've found two outcomes where each player wins exactly once:1. Alice beats Bob, Bob beats Conway, Conway beats Alice.2. Alice loses to Bob, Bob loses to Conway, Conway loses to Alice.Is there a third one? Let me think.If I try to think of another arrangement, but I can't seem to find one. Because in each case, if one player wins two matches, the other two can't both have one win each. So, it seems like there are only two favorable outcomes.Therefore, out of the total 8 possible outcomes, only 2 of them result in each player winning exactly once. So, the probability is 2/8, which simplifies to 1/4.Wait, but let me double-check to make sure I haven't missed any other favorable outcomes.Let me list all 8 possible outcomes explicitly:1. Alice beats Bob, Bob beats Conway, Conway beats Alice. (Each wins once)2. Alice beats Bob, Bob beats Conway, Alice beats Conway. (Alice wins twice)3. Alice beats Bob, Conway beats Bob, Conway beats Alice. (Conway wins twice)4. Alice beats Bob, Conway beats Bob, Alice beats Conway. (Alice wins twice)5. Bob beats Alice, Bob beats Conway, Conway beats Alice. (Bob wins twice)6. Bob beats Alice, Bob beats Conway, Alice beats Conway. (Bob wins twice)7. Bob beats Alice, Conway beats Bob, Conway beats Alice. (Conway wins twice)8. Bob beats Alice, Conway beats Bob, Alice beats Conway. (Each wins once)So, from this list, only outcomes 1 and 8 satisfy the condition that each player wins exactly once. So, that's 2 out of 8, which is indeed 1/4.Therefore, the probability that each player wins exactly once is 1/4.
âLet a=0.7^{0.4}, b=0.4^{0.7}, c=0.4^{0.4}. Then, the relationship among a, b, and c is (ã).A: b < a < cB: a < c < bC: b < c < aD: c < b < a
đĄOkay, so I have this problem where I need to compare three numbers: a, b, and c. They are defined as follows:- a = 0.7^{0.4}- b = 0.4^{0.7}- c = 0.4^{0.4}And I need to figure out the relationship among them. The options are:A: b < a < c B: a < c < b C: b < c < a D: c < b < aHmm, let me think about how to approach this. I remember that when dealing with exponents, especially with numbers between 0 and 1, the behavior can be a bit tricky. So, I need to recall some properties of exponents and maybe logarithms to compare these values.First, let me write down the values again to make sure I have them right:- a = 0.7^{0.4}- b = 0.4^{0.7}- c = 0.4^{0.4}I notice that both a and c have the same base, 0.4, but different exponents. Similarly, a and b have the same exponent, 0.4 and 0.7 respectively, but different bases. So, maybe I can compare them in pairs.Let me start by comparing a and c because they have the same base. So, a = 0.7^{0.4} and c = 0.4^{0.4}. Since both are raised to the 0.4 power, I can compare the bases directly. I know that for numbers between 0 and 1, as the base increases, the result of the exponentiation also increases, but since the exponent is less than 1, the effect is a bit different. Wait, actually, when you have a number between 0 and 1 raised to a power less than 1, it actually increases the value. For example, 0.25^{0.5} is 0.5, which is larger than 0.25. So, in this case, since 0.7 is larger than 0.4, and both are raised to the 0.4 power, a should be larger than c. So, a > c.Okay, that's one comparison. Now, let's compare b and c. Both b and c have the same base, 0.4, but different exponents. b is 0.4^{0.7} and c is 0.4^{0.4}. Since the base is between 0 and 1, raising it to a higher exponent will make the result smaller. So, because 0.7 is larger than 0.4, b should be smaller than c. Therefore, b < c.So far, I have a > c and b < c. That means a is the largest, then c, and then b is the smallest. So, putting it all together, the order should be b < c < a.Let me double-check to make sure I didn't make a mistake. Maybe I can take the natural logarithm of each to compare them more precisely.Taking ln(a) = ln(0.7^{0.4}) = 0.4 * ln(0.7) Similarly, ln(c) = ln(0.4^{0.4}) = 0.4 * ln(0.4) And ln(b) = ln(0.4^{0.7}) = 0.7 * ln(0.4)Since ln(0.7) and ln(0.4) are both negative numbers (because the arguments are less than 1), multiplying them by positive exponents will keep them negative.Calculating the approximate values:ln(0.7) â -0.3567 ln(0.4) â -0.9163So,ln(a) â 0.4 * (-0.3567) â -0.1427 ln(c) â 0.4 * (-0.9163) â -0.3665 ln(b) â 0.7 * (-0.9163) â -0.6414Now, exponentiating these to get back to the original values:a â e^{-0.1427} â 0.867 c â e^{-0.3665} â 0.693 b â e^{-0.6414} â 0.527So, numerically, a â 0.867, c â 0.693, and b â 0.527. Therefore, the order is indeed b < c < a, which confirms my earlier conclusion.I think that makes sense. So, the correct option is C: b < c < a.**Final Answer**boxed{C}