令x=2tanu,则dx=2sec²u du,u=arctan(x/2)
∫ 1/(√（x²+4)³)dx
=∫2sec²u/(√(4tan²u+4)³) du
=∫2sec²u/(√(4³(sec³u)²) du
=∫2sec²u/(8sec³u) du
=(1/4)∫(1/secu)du
=(1/4)∫cosu du
=sinu/4+C
=sin[arctan(x/2)]/4+C
=x/[4√(x²+4)]+C
C为任意常数