Find a cubic function f(x)=ax^3+cx^2+d that has a local maximum value of 9 at -4 and a local minimum value of 6 at 0.

Question

Find a, c, and d.

Answer 1

f'(-4) = 9
f'(0) = 6

f'(x) = 3ax^2 + 2cx

f'(-4) = 48a - 8c = 9
f'(0) = 0 + 0 = 6

Oh, oh, something fishy here.
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