f(x)=2x^3+3x^2-12x+1
f'(x)=6x^2+6x-12
f"(x)=12x+6
f'(x)=0即6x^2+6x-12=0
x^2+x-2=0
解得x1=-2,x2=1
f'(-2)=0
f"(-2)=-24+6