akl3644 3 years ago Calculate an integral

1. akl3644

2. vf321

Have you tried u-sub?

3. vf321

try u = 9-x^2

4. jamesHayek

No, sub u=x^2

5. vf321

I'm pretty sure mine still works... Both are fine...

6. akl3644

my substitution become like this...

7. vf321

Well you can trig sub if you want but that makes it needlessly complicated IMO.

8. akl3644

emm what u suggest ?

9. vf321

I told u. u = 9-x^2.

10. vf321

Do you know how to u-sub?

11. jamesHayek

$u=x^2; \frac{ 1 }{ 2 }du = xdx$

12. vf321

Again, either mine or james' work, since he keeps insisting....

13. jamesHayek

you will get: $\frac{ 1 }{ 2 }\int\limits_{0}^{1.6}(9-u)^{3/2}u du$

14. jamesHayek

for the integrand $(9-u)^{3/2}u$ sub s=9-u and ds=-du

15. jamesHayek

at this point you can expand the integrand and solve.

16. vf321

@jamesHayek I msged you but I'll tell you again: We don't want to give them most of the problem.

17. jamesHayek

vf321, this is a site to help. Not bicker. Show your work to help her.

18. vf321

@jamesHayek help, not do homework for. But fine, this is not getting us anywhere. Let's stop arguing.

19. akl3644

i am following ur step now. thx. trying to get the right answer

20. akl3644

i will try both method