另lnx=t,x=e^t
∫lnx²dx
=∫2lnxdx
=2∫lnxdx
=2∫xlnxdlnx
=2∫(e^t)·tdt
=2∫td(e^t)
=2[(e^t)·t-∫(e^t)dt]
=2[(e^t)·t-(e^t)]+C
=2(e^t)·(t-1)+C
=2x(lnx-1)+C