∫x(3-x^2)^3dx=1/2∫(3-x^2)^3*2xdx=1/2∫(3-x^2)^3dx^2=-1/2∫(3-x^2)^3d(-x^2)=-1/2∫(3-x^2)^3d(3-x^2)=-1/2* 4*(3-x^2)^4+C=-2(3-x^2)^4+C
