∫xf(x)dx=∫xd(xlnx)=x^2lnx-∫xlnxdx=x^2lnx-1/2∫lnxd(x^2)=x^2lnx-1/2x^2lnx+1/2∫x^2d(lnx)
=1/2x^2lnx+1/2∫xdx=1/2x^2lnx+1/4x^2=x^2(1/2lnx+1/4)
B
∫xf(x)dx=∫xd(xlnx)=x^2lnx-∫xlnxdx=x^2lnx-1/2∫lnxd(x^2)=x^2lnx-1/2x^2lnx+1/2∫x^2d(lnx)
=1/2x^2lnx+1/2∫xdx=1/2x^2lnx+1/4x^2=x^2(1/2lnx+1/4)
B