## jennychan12 3 years ago antiderivative of (x^2+4x)^1/3 ?

1. jennychan12

$\sqrt[3]{x^2+4x}$

2. jennychan12

i know that u = x^2+4x so du = (2x+4)dx where do i go from there?

3. jennychan12

@agent0smith @Dido525

4. AtiFS

well u multipl that by 1/3 too

5. AtiFS

1/3 dx (x^2 + 4x) = 1/3* (2x + 4)..I think so

6. jennychan12

how did you get that? can u explain?

7. jennychan12

cuz du = (2x+4)dx = (2(x+2))dx so 1/2du = (x+2)dx then...?

8. AtiFS

actually, the value of power multplies..hmm du = 1/3*(2x + 4)dx => 3*du = (2x + 4)dx

9. zepdrix

I'm pretty sure you need to either do a Trig-Sub, or Integration-By-Parts might also be possible. No U-Sub available though :( Have you learned either of those methods yet?

10. jennychan12

yeah the substitution method.

11. zepdrix

Trig subs? :D

12. jennychan12

i think so? remind me what that is?

13. Kainui

I think you might want to add and subtract +4 and -4 under the cube root so that you can factor.

14. AtiFS

google the concept behind it :)

15. beginnersmind

idk how to do this, I'm just posting so that I get notified when someone answers it.

16. Kainui

I could reduce it down so that it becomes $2^{3/5}\int\limits_{}^{}\tan^{3/5} \theta \sec \theta d \theta$ after making the substitution: $(x+2)=2\sec \theta$

17. Kainui

the fraction should be 5/3 not 3/5 on the 2 and tan(theta)

18. AtiFS

19. Kainui

I can't seem to crack it. You're in calculus 1 or 2?

20. jennychan12

1

21. jennychan12

where did the tangent, secant stiff come from?

22. zepdrix

Ah sorry I was busy :C Kanoo been helping you? c:

23. Kainui

I was doing trigonometric substitution, but you don't learn that until cal 2. If there's an easier way with just using u-sub then I would be surprised! Good luck zeppy! =P

24. zepdrix

Ya I dunno sorry Jenny :c This doesn't seem like a problem you should be doing yet, hmm.

25. Kainui

Check this out: http://www.wolframalpha.com/input/?i=(x%5E2%2B4x)%5E1%2F3dx&t=crmtb01 I've never even heard of that stuff. Hypergeometric function? lol

26. zepdrix

Woah that looks fun :O

27. jennychan12

oy.....! -_-

28. cinar

|dw:1355977140299:dw|

29. cinar

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30. cinar

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31. cinar

the last sub. should be u=2cosht

32. cinar

@satellite73 @Zarkon

33. cinar
34. cinar

I do not have enough information to solve this question..

35. jennychan12

g is the antiderivative function if g(5) = 7, then g(1) = ?

36. cinar

why are giving this info now, you should mention this at the beginning.. come on..

37. cinar

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38. cinar
39. cinar
40. jennychan12

thanks for trying to help. :)