f'(x)=e^x+(x+1)e^x=(x+2)e^x,定义域为实数集,x<-2时f'(x)<0,x>-2时,f'(x)>0,因此f(x)在(-∞,-2)上递减,在(-2,+∞)上递增f'(x)=e^x+(x+k)e^x=(x+k+1)e^x,f(x)在(-∞,-k-1)上递减,在...