令u=lnx,x=e^u,dx=e^u du
故∫(0,3) dx/[x√(4-lnx)]
=∫(0,3)e^u/[e^u·√(4-u)] du
=∫(0,3)1/√(4-u) du
=-2√(4-u)|(0,3)
=-2+2×2
=2