## anonymous 5 years ago If integral from 0,2 (2x^3-kx^2+2x)dx=12, then k must be? I've tried working it out several times but I still don' get the right answer.

1. anonymous

$\int\limits_{}^{?}$

2. anonymous

$int_{0}{2}$

3. anonymous

$\int\limits_{0}^{2} (2x^3-kx^2+2k) dx =12$

4. anonymous

$\int\limits_{0}^{2} 2x^3 - kx^2 + 2k = 12$

5. anonymous

= 2x^4/4 - kx^3/3 +2kx from 2 to 0 , = 12

6. anonymous

2(2^4)/4 - k(2^3)/3 + 2(k)(2) - [ 0 + 0 + 0 ] = 12

7. anonymous

did you get that so far?

8. anonymous

yeah... instead of adding one to the power I was just finding the derivative..

9. anonymous

well we are integrating, correct

10. anonymous

give me a medal

11. anonymous

yeah :) thanks... let me see if i get it now

12. anonymous

Got it :)

13. anonymous

:)

14. anonymous

hey can u help me in another one real quick? sorry

15. anonymous

ok

16. anonymous

$\int\limits_{}^{} (\sec^2x)(\tan ^2x)dx=$

17. anonymous

u = tan x

18. anonymous

du = sec^2 x

19. anonymous

so you do u sub?

20. anonymous

yep

21. anonymous

ok thanks

22. anonymous

so i got integral u^2 du