令f'(x)=3x^2-6x-9=0
x^2-2x-3=0
x=3或-1
f(-3)=-27-27+27+5=-22,
f(-1)=-1-3+9+5=10,
f(-4)=-64-48+36+5=-71
f(4)=64-48-36+5=-19
最大值为10,最小值为-71
令f'(x)=3x^2-6x-9=0
x^2-2x-3=0
x=3或-1
f(-3)=-27-27+27+5=-22,
f(-1)=-1-3+9+5=10,
f(-4)=-64-48+36+5=-71
f(4)=64-48-36+5=-19
最大值为10,最小值为-71