# Math Help - indefinite integral

1. ## indefinite integral

I have no idea why the homework is telling me I'm getting the wrong answer.. I'm following exactly how they did it in the book.. Let me know what you guys get

Evaluate the indefinite integral:
___________

2. Did you get something like: $\frac{1}{12}\cdot (2x+9)^{6} + C$

They didn't expand the silly binomial, did they?

3. Originally Posted by TKHunny
Did you get something like: $\frac{1}{12}\cdot (2x+9)^{6} + C$

They didn't expand the silly binomial, did they?
nope i guess not I kept getting (1/30) instead of (1/12)

4. Hmmm... Where does that leave us? Did the book get it right?

5. Originally Posted by tbenne3
I have no idea why the homework is telling me I'm getting the wrong answer.. I'm following exactly how they did it in the book.. Let me know what you guys get

Evaluate the indefinite integral:
___________
let $u = 2x+9 \implies du = 2 dx \implies dx=\frac{du}{2}$

substitute $u$ , $dx$ in your question and integrate. You should end up with the expression provided by TKHunny in post#2

6. Originally Posted by tbenne3
I have no idea why the homework is telling me I'm getting the wrong answer.. I'm following exactly how they did it in the book.. Let me know what you guys get

Evaluate the indefinite integral:
___________
I don't see any way to tell what you are doing wrong if you don't show what you are doing!

7. Originally Posted by tbenne3
I have no idea why the homework is telling me I'm getting the wrong answer.. I'm following exactly how they did it in the book.. Let me know what you guys get

Evaluate the indefinite integral:
___________
1/12*(2*x+9)^6

8. Originally Posted by mahm32
1/12*(2*x+9)^6
Thats exactly what TKHunny has said in post number 2.

Isn't your book following the substution method?

let $u = 2x+9 \implies du = 2 dx \implies dx=\frac{du}{2}$

$\int (2x+9)^5 dx = \int u^5 \frac{du}{2} = \frac{1}{2} \int u^5 du$
now integrate, and substitute $u=2x+9$ after your integration is complete!