Question

I have the answer can somone please check me
Find values for a and b so that
f(x)=x^3+ax+b
has a relative minimum at (2,-9)
a=? b=?

Answer 1

\[f'(x)=3x^2+a\]

Answer 2

you want the min at \(x=2\) so set
\[3\times 2^2+a=0\] and solve for \(a\)

Answer 3

a=12

Answer 4

i think \(a=-12\)

Answer 5

ok yes it is -12

Answer 6

so then how do I get b

Answer 7

satellite73 can you help me please