Int[(x^3)/((e^x)-1)] [0, infinity](adsbygoogle = window.adsbygoogle || []).push({});

What is the trick?

I thought of by-parts but how would you integrate 1/((e^x)-1)?

Substitution won't work with

u = e^x -1

with x = ln|u+1|

or it would be rather tough to evaluate u^3

Someone please give me a hint.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Improper Integral trick

**Physics Forums | Science Articles, Homework Help, Discussion**