# Evaluate integral of 3e^(-x) with respect to x

Since is constant with respect to , move out of the integral.
Let . Then , so . Rewrite using and .
Let . Find .
Differentiate .
Since is constant with respect to , the derivative of with respect to is .
Differentiate using the Power Rule which states that is where .
Multiply by .
Rewrite the problem using and .
Since is constant with respect to , move out of the integral.
Multiply by .
The integral of with respect to is .
Simplify.
Replace all occurrences of with .
Evaluate integral of 3e^(-x) with respect to x