解由g(x)=e^x*f(x)
=e^x*(x³-3x²)
求导函数
g'(x)=[e^x*(x³-3x²)]'
=(e^x)'(x³-3x²)+(e^x)(x³-3x²)'
=(e^x)(x³-3x²)+(e^x)(3x²-6x)
=(e^x)(x³-6x)
=(e^x)(x²-6)x
=(e^x)(x-√6)(x+√6)x
令g'(x)=0
解得x=√6或x=-√6或x=0
当x属于(√6,正无穷大),f'(x)>0
当x属于(0,√6),f'(x)<0
当x属于(-√6,0),f'(x)>0
当x属于(负无穷大,-√6),f'(x)<0
即函数g(x)=e^x*f(x)的单调增区间(√6,正无穷大)和(-√6,0).
函数g(x)=e^x*f(x)的单调减区间(0,√6)和(负无穷大,-√6).