证明:作辅助函数F(x)=f(x)e∧g(x)则F'(x)=f'(x)e∧g(x)+f(x)g'(x)e∧g(x) =[f'(x)+f(x)g'(x)]e∧g(x)显然F(x)在[a,b]上连续,在(a,b)上可导,且F(a)=F(b)=0由罗尔定理知,至少存在c∈(a,b),使F'(c)=0即 [f'(c)+f(c)g'(c)]e∧g(c)=0而 e∧g(c)≠0故 f'(c)+f(c)g'(c)=0.