simple one

find the values of 'a' for which the function f(x)=(a+2)x³ -ax²+9ax-1 is monotonically decreasing for x eR

iknow its very easy but i m not getting the ans

i did f'(x)â‰¤0

and afetr taht D<=0

not getting ans with it

any other case also required??

5 Answers

for monotonically decreasing ,,,,,f'(x) < 0....you have a wrong assumption...,f'(x) â‰¤ 0.

no its f'(x)â‰¤0 only for monotonically decreasing

and f'(X)<0 is for strictly decreasing

so we need a word "strictly", in this case to avoid confusion ....was it there?

why strictly......its given monotonically

For the quad ax^2+bx+c to be â‰¤0, a<0.

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