解:原式=(1/3)∫x^2de^3x=(1/3)(x^2*e^3x-2∫e^3x*xdx)+C=(1/3)(x^2*e^3x-(2/3)∫xde^3x)+C=(1/3)(x^2*e^3x-(2/3)(x*e^3x-(1/3)∫de^3x))+C=(1/3)(x^2*e^3x-(2/3)(x*e^3x-(1/3)*e^3x))+C=e^3x*((1/3)*x^2-(2/3)*x+2/9) +C
多次就可以分部积分可以解决