# Substitution Rule for Indefinite Integrals

1. May 27, 2008

### temaire

1. The problem statement, all variables and given/known data
$$\int2e^-^7^xdx$$

2. Relevant equations
None

3. The attempt at a solution

$$(\frac{-2}{7})(\frac{e^-^7^x}{-7})+C$$

This is as far as I can go, but the answer is:

$$\frac{-2e^-^7^x}{7}+C$$

2. May 27, 2008

### rocomath

How did you get two 1/7 terms?

3. May 27, 2008

### temaire

I took the antiderivative of $$e^-^7^x$$.

4. May 27, 2008

### rocomath

So, why do you have 1/7 * 1/7? Just do it again from scratch and you'll probably see what you did wrong.

5. May 27, 2008

### rocomath

$$2\int e^{-7x}dx$$

$$-\frac 2 7\int -7e^{-7x}dx$$

You don't need to divide by another -7. It's already in standard form!

6. May 27, 2008

### temaire

I've got it now, thanks.