Question

已知函数f(x)=x3-3x2-9x,求f(x)的单调区间

Answer 1

∵f(x)=x3-3x2-9x

∴f'(x)=3(x^2+2x-3)

令f'(x)=3(x^2+2x-3)=0

则f'(x)的零点为 x=-3 x=1

所以f(x)的单调增区间是 x=1

f(x)的单调减区间：-3