∫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
