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If the roots of `x^(5) - 40 x^(4) + Px^(3) + Qx^(2) + Rx + S = 0` are in G.P. and sum of their reciprocals is 10, then |S| is equal toA. 4B. -4C. 8D. none of these |
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Answer» Correct Answer - D Let the roots be `(a)/(r^(2)), (a)/(r), a, ar, ar^(2)` Then, `a((1)/(r^(2))+(1)/(r)+1+r+r^(2))=40" "...(i)` It is given that `(1)/(a)(r^(2)+r+1+(1)/(r)+(1)/(r^(2)))=10" "...(i)` From (i) and (ii), we get `a^(2) = 4 rArr a = +- 2` Now, Product of the roots = -S `rArr" "a^(5) = - S rArr S = +- 32 rArr |S| = 32` |
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