For which value (s) of a f (x )=-x^3+4ax^2+2x-5 is decreasing for every x ?

Question

Accepted Answer

Correct answer: D. (d) f (x )=-x^3+4ax^2+2x-5f^ ' (x )=-3x^2+8 ax+2 for decreasing f^ ' (x )<0 Discriminant of f^ ' (x )= (8a )^2-4 (-3 ) (2 )=64a^2+24>0 , ∀a ∈R Hence, f (x ) is decreasing for no value of a.

$For which value (s) of a f (x) = - x^{3} + 4 a x^{2} + 2 x - 5 is decreasing for every x ?$

Solution

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