f′(x)=3x²-6x-9=3(x-3)(x+1)
∴f(x)在[-1,3]单调减,其余单调增
f(-4)=-71
f(-1)=10
f(3)=-22
f(4)=-15
∴最大值为f(-1)=10,最小值为f(-4)=-71