∫xe-xdx=∫xedx-∫xdx=e∫xdx-∫xdx=ex²/2-x²/2
原式为（e*1²/2-1²/2）-（e*0²/2-0²/2）=e/2-1/2=2.718/2-1/2=1.359-0.5=0.859