求导数,f'(x)=3x^2-2ax,令f'(x)=3x^2-2ax=0,求得:x=0,x=2a/3,然后对a进行分析,
(1)a0时,当0x2a/3时,f'(x)=3x^2-2ax0,f(x)单调递减,反之则f(x)单调递增;
(2)a0时,当2a/3x0时,f'(x)=3x^2-2ax0,f(x)单调递减,反之则f(x)单调递增;
(3)a=0时,f'(x)=3x^2-2ax=0,f(x)在定义域上单调递增;
求导数,f'(x)=3x^2-2ax,令f'(x)=3x^2-2ax=0,求得:x=0,x=2a/3,然后对a进行分析,
(1)a0时,当0x2a/3时,f'(x)=3x^2-2ax0,f(x)单调递减,反之则f(x)单调递增;
(2)a0时,当2a/3x0时,f'(x)=3x^2-2ax0,f(x)单调递减,反之则f(x)单调递增;
(3)a=0时,f'(x)=3x^2-2ax=0,f(x)在定义域上单调递增;