take xn +1 as t.
differentiating, n xn-1 dx = dt
substitute.
we get dt/n xn-1 x (t)
=dt/n xn t
=dt/n t (t-1)
now you can integrate using partial fractions.
At + B(t-1)=1
A=-1, B=1
so, we get (-1) dt/t +dt/(t-1)
= -ln t + ln(t-1)
= - ln (xn + 1) + ln xn +c
=ln [(xn + 1)/xn] = ln [1+1/xn] +c