## 3psilon 2 years ago How to integrate (6-2x)^2 . (indefinite integral). I'm trying U sub but Idk what I'm doing wrong

1. TuringTest

what did you use for u ?

2. 3psilon

6-2x

3. TuringTest

can you show your sork? what did you get for du? what did you get for dx?

4. 3psilon

U = 6-2x du = -2dx $(1/2) \int\limits_{}^{} -2U^2dx$ @TuringTest

5. TuringTest

I'm not seeing where you get the -2 from... u=6-2x du=-2dx -> dx=-du/2

6. 3psilon

It's to get du right ? so I multiply by 1 pretty much 2/2

7. TuringTest

you have left your integral all mixed up with u integrated with respect to x; you can't do that. I think you are getting confused there. you need to sub in the values: u=6-2x du=-2dx -> dx=-du/2 subbing in for u and dx gives$\int u^2(-\frac{du}2)=-\frac12\int u^2du$

8. 3psilon

Ohhh thank you turing!

9. TuringTest

Welcome!

10. 3psilon

We weren't taught how to solve for dx and plug back in but I like that way!

11. TuringTest

I sort of never saw them do it in class that way either, I never understood why :p

12. 3psilon

@TuringTest What answer are you getting ? I get $\frac{-(6-2x)^{3}}{6} +c$ But my TI-89 is giving me$\frac{4(x-3)^{3}}{3} +C$

13. TuringTest

it is the same answer; they appear to have factored out a -2 in your TI-89

14. 3psilon

Ohh okay! Thanks! :)