Consider the indefinite integral ${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{-6e^{-6x}}{(e^{-6x}+2{)}^6}dx$ :

This can be transformed into a basic integral by letting

$u=$ and

$du=dx$

Performing the substitution yields the integral

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}du$