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Find the value of `a`for which the sum of the squares of the roots of the equation `x^2-(a-2)x-a-1=0`assumes the least value. |
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Answer» Correct Answer - B Let `alpha, beta` be the roots of the given equation. Then, `alpha + beta = a -2 and alpha beta = - (a+1)`. `therefore" "alpha^(2)+beta^(2)=(alpha+beta)^(2)-2 alpha beta = (a-2)^(2) + 2(a+1)` `rArr" "alpha^(2) + beta^(2) = a^(2) - 2a + 6 = (a-1)^(2) + 5` Clearly, `alpha^(2) + beta^(2) ge 5`. So, the minimum value of `alpha^(2)+beta^(2)` is 5 which it attains at = 1. |
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