If f (x) = ax ^ 3 + 3mx ^ 2 + NX + m ^ 2 has an extreme value of 0 when x = - 1, then M + n =? Note that the third power of X is preceded by A

If f (x) = ax ^ 3 + 3mx ^ 2 + NX + m ^ 2 has an extreme value of 0 when x = - 1, then M + n =? Note that the third power of X is preceded by A

When A0, there is no solution,
When a = 0, M + n = 21