# Integral of statistical mechanics

1. Apr 14, 2013

### alejandrito29

Hello, i need solve de following integral

$$\int ^{\infty}_0 \frac{x^3}{e^x+1} dx$$

i tried with the fermi function but the factor $$e^x$$ is different to $$e^{x-\eta}$$, and with the gamma function but the factor $$e^x+1$$ is different to $$e^x-1$$.