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question:it possible to place 10 blue points, 10 red points, and 10 green points in the plane such that the distances between any two points are pairwise distinct and that triangleright for each blue point, the second closest point is red; triangleright for each red point, the second closest point is green; triangleright for each green point, the second closest point is blue?

answer:1. **Arrangement of Points:** We start by arranging the points on a straight line from left to right. Label these points in order as (A_1, A_2, ldots, A_{30}), and assign colors as follows: - Points (A_{3k+1}) are blue. - Points (A_{3k+2}) are green. - Points (A_{3k+3}) are red for (0 leq k leq 9). 2. **Defining Distances:** Let (d_i) be the distance between (A_i) and (A_{i+1}) for (1 leq i leq 29). Our goal is to find positive values for ((d_i)_{1 leq i leq 29}) such that all pairwise distances between the points are distinct and the following constraints are satisfied: - For each blue point, the second closest point is red. - For each red point, the second closest point is green. - For each green point, the second closest point is blue. 3. **Initial Placement and Verification of Points:** Set (A_1) at position 0 on a graduated line. Place (A_i) at the position: [ A_i = d_1 + d_2 + cdots + d_i. ] This guarantees that the distance between (A_i) and (A_{i+1}) is (d_i) for (1 leq i leq 29). 4. **Ensuring Distance Conditions:** To ensure the conditions are met, assign (d_i = frac{1}{i+2}) for (1 leq i leq 27): [ d_i < d_{i-1} quad text{and} quad d_i + d_{i+1} > d_{i-1}. ] Compute (d_i + d_{i+1} - d_{i-1}): [ begin{aligned} d_i + d_{i+1} - d_{i-1} &= frac{1}{i+2} + frac{1}{i+3} - frac{1}{i+1} &= frac{(i+1)(i+3) + (i+1)(i+2) - (i+2)(i+3)}{(i+1)(i+2)(i+3)} &= frac{(i+1)^2 + 3(i+1) + (i+1)^2 + 2(i+1) - (i^2 + 5i + 6)}{(i+1)(i+2)(i+3)} &= frac{i^2 + 4i + 4}{(i+1)(i+2)(i+3)} &= frac{(i+2)^2 - 2}{(i+1)(i+2)(i+3)} > 0. end{aligned} ] 5. **Adjustments for Distinct Distances:** If some distances are not distinct, adjust (d_i) slightly. For each (i) from 1 to 27, modify (d_i) such that: [ d_i < d_{i-1} quad text{and} quad d_i + d_{i+1} > d_{i-1} ] while preserving the distinctness of previous (d_j). 6. **Placing Points A_28 and A_29:** Ensure that the distance between (A_{28}) and (A_{29}) is greater than (d_{27}), yet distinct from the other distances. Place (A_{29}) (red) at: [ d_{28} quad text{such that} quad d_{27} < d_{26} < d_{27} + d_{28}. ] 7. **Placing the Last Point A_30:** Place (A_{30}) (green) such that: [ d_{29} quad text{such that} quad d_{28} + d_{27} > d_{29} > d_{28}. ] Adjust (d_{29}) to maintain distinctness and still satisfy: [ d_{28} + d_{27} > d_{29} > d_{28}. ] 8. **Verification:** Check: - For (A_{30}), the second closest point is (A_{28}) using (d_{28} + d_{27} > d_{29}). - For (A_{29}), the second closest point is (A_{27}) using (d_{28} + d_{27} > d_{29}). # Conclusion: It is possible to arrange the points such that all conditions are satisfied. Thus, the final answer is: (boxed{text{Yes, it is possible.}})

question:The function ( F(x) = left| cos^2 x + 2 sin x cos x sin^2 x + Ax + B right| ) on ( 0 leq x leq frac{3}{2} pi ) attains a maximum value ( M ) that depends on parameters ( A ) and ( B ). For which values of ( A ) and ( B ) is ( M ) minimized? Prove your conclusion.

answer:To find the values of ( A ) and ( B ) that minimize the maximum value ( M ) of the function ( F(x) ) over the interval ( 0 leq x leq frac{3}{2}pi ), let's analyze the given function: [ F(x) = left| cos^2 x + 2 sin x cos x - sin^2 x + A x + B right| ] 1. **Rewriting the Trigonometric Part:** The expression inside the absolute value can be rewritten using trigonometric identities as: [ begin{aligned} cos^2 x + 2 sin x cos x - sin^2 x &= (cos x)^2 + 2 (sin x)(cos x) - (sin x)^2 &= cos^2 x + 2 sin x cos x - sin^2 x &= cos^2 x - sin^2 x + 2 sin x cos x &= cos(2x) + sin(2x) &= sqrt{2} sin(2x + frac{pi}{4}), end{aligned} ] where we used the identity (cos(2x) = cos^2 x - sin^2 x) and (sin(2x) = 2 sin x cos x). Thus we can rewrite ( F(x) ) as: [ F(x) = left| sqrt{2} sin left(2x + frac{pi}{4}right) + A x + B right| ] 2. **Case Analysis for ( A = 0 ) and ( B = 0 ):** If ( A = 0 ) and ( B = 0 ), then: [ F(x) = left| sqrt{2} sin left(2x + frac{pi}{4}right) right| ] We know that (left| sin left(2x + frac{pi}{4} right) right| leq 1), hence: [ F(x) = sqrt{2} left|sin left(2x + frac{pi}{4}right) right| leq sqrt{2} ] The maximum value ( M ) for ( F(x) ) in the interval ( 0 leq x leq frac{3}{2}pi ) is ( sqrt{2} ). Hence, ( M = sqrt{2} ). 3. **Exploring Other Values of ( A ) and ( B ):** We will analyze how ( F(x) ) behaves for different values of ( A ) and ( B ): - **Case 1: ( A = 0 ), ( B neq 0 )** In this case, the function becomes: [ F(x) = left| sqrt{2} sin left(2 x + frac{pi}{4} right) + B right| ] Clearly, the maximum value of ( F(x) ) will be greater than ( sqrt{2} ) if ( B neq 0 ) because the absolute value would have to account for the term ( B ). - **Case 2: ( A > 0 ), ( B geq 0 )** Evaluate ( Fleft(frac{pi}{8} right) ): [ Fleft( frac{pi}{8} right) = sqrt{2} sin left( frac{pi}{4} + frac{pi}{4} right) + left( frac{pi}{8} right) A + B = sqrt{2} + frac{pi}{8} A + B ] Since ( A > 0 ) and ( B geq 0 ), it is evident that (sqrt{2} + frac{pi}{8} A + B > sqrt{2} ), thus making ( M > sqrt{2} ). - **Case 3: ( A > 0 ), ( B < 0 )** - If ( |B| < frac{9pi}{8} A ), [ left| sqrt{2} + frac{9 pi}{8} A + B right| > sqrt{2} ] - If ( |B| geq frac{9pi}{8} A ), [ left| -sqrt{2} + frac{5 pi}{8} A + B right| > sqrt{2} ] In both cases, ( M > sqrt{2} ). - **Case 4: ( A < 0 ), ( B leq 0 )** Evaluate ( Fleft(frac{5 pi}{8} right) ): [ Fleft( frac{5 pi}{8} right) = left|- sqrt{2} + frac{5 pi}{8} A + B right| > sqrt{2} ] - **Case 5: ( A < 0 ), ( B > 0 )** - If ( B > -frac{5 pi}{8} A ), [ left| -sqrt{2} + frac{5 pi}{8} A + B right| > sqrt{2} ] - If ( B geq -frac{pi}{8} A ), [ Fleft( frac{pi}{8} right) = left| sqrt{2} + frac{pi}{8} cdot A + B right| > sqrt{2} ] In conclusion, the only way to ensure the minimum ( M ) is attaining its minimum value (which is ( sqrt{2} )) is by setting ( A = 0 ) and ( B = 0 ). [ boxed{A = 0 text{, } B = 0} ]

question:a modified game of Deal or No Deal, participants choose a box at random from a set of 30 boxes, each containing one of the following values: [ begin{tabular}{|c|c|} hline 0.05 & 500 hline 2 & 1,000 hline 10 & 2,000 hline 20 & 5,000 hline 50 & 10,000 hline 75 & 20,000 hline 100 & 50,000 hline 150 & 75,000 hline 200 & 100,000 hline 250 & 200,000 hline 300 & 300,000 hline 350 & 400,000 hline 400 & 500,000 hline 450 & 750,000 hline 500 & 1,000,000 hline end{tabular} ] Determine the minimum number of boxes a participant needs to eliminate in order to have a onethird chance of holding at least 75,000 as their chosen box.

answer:From the table, the boxes containing at least 75,000 are: 75,000, 100,000, 200,000, 300,000, 400,000, 500,000, 750,000, 1,000,000. This totals 9 boxes. To have at least a one-third chance of holding such a box, we need the condition P(text{holding at least 75,000}) geq frac{1}{3}. If there are x boxes left (including the chosen one), the probability of the chosen box containing at least 75,000 should be frac{9}{x} geq frac{1}{3}. Solving for x, we have: [ 9/x geq 1/3 implies x leq 27 ] Thus, there need to be at most 27 boxes, including the one held by the participant. Since we start with 30 boxes, the participant must eliminate at least 30 - 27 = boxed{3} boxes to have at least a one-third chance of holding a box containing at least 75,000.

question:Simplify (17a + 45b) + (15a + 36b) (12a + 42b) 3(2a + 3b).

answer:First distribute the negative sign and handle the expression inside the parentheses: [ (17a + 45b) + (15a + 36b) - (12a + 42b) - 3(2a + 3b) = 17a + 45b + 15a + 36b - 12a - 42b - 6a - 9b ] Now, combine like terms: [ 17a + 15a - 12a - 6a = 14a ] [ 45b + 36b - 42b - 9b = 30b ] The final simplified expression is: [ boxed{14a + 30b} ]

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