How do you integrate exex using substitution?

1 Answer
Nov 20, 2016

exexdx

Method 1 - Immediate Substitution

Make the substitution u=ex, which implies that du=exdx, so

exexdx=(ex)(exdx)=udu=u22=(ex)22=e2x2+C

Method 2 - Simplification, then Substitution

Use the rule ab(ac)=ab+c to rewrite the integral as

exexdx=e2xdx

Now substitute u=2x so du=2dx:

e2xdx=12(e2x)(2dx)=12eudu

Since eudu=eu:

12eudu=12eu=eu2=e2x2+C