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## onegirl 2 years ago Evaluate the definite integral.

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1. onegirl

2. skylarxoxoxo

go into this site callec web 2.0 calc it type the problem into the calculator and BAM theres the answer! :) or better yet, get out paper and actually write out the problem

3. skylarxoxoxo

and solve it that way

4. Loser66

@onegirl do you have any idea?

5. onegirl

am i just going to substitute u or?

6. Loser66

yes, which one? u =?

7. Loser66

try u = x^2 +1 then du =?

8. onegirl

is du the derivative of it? or

9. Loser66

yes!! try, if you make some mistake, i correct it then, but the most important is trying!!

10. onegirl

ok

11. Loser66

don't worry, I dare not say anything further, but to this problem, I am ok

12. onegirl

okay i'll try it t

13. onegirl

okay for the derivative i got 2x

14. Loser66

2xdx girl. ok, let put it in neat du = 2x dx , right?

15. Loser66

got it?

16. onegirl

okay

17. Loser66

ok, now, we change the limit, have to. tell me, if x =0, u =?

18. Loser66

do you know what I am doing?

19. onegirl

hmmm no

20. Loser66

ok, let me explain. Originally, you have x, dx and limits respect to x then, you change (substitute) to u, so, dx must change to du and limits must follow u, right?

21. onegirl

yes

22. onegirl

so u will be 0 too right?

23. onegirl

Me? I live in USA

24. Loser66

ok, take step!! forget my question, I thought you don't understand what I mean so, made that question to find out another way for you to come up the problem, now, you got it, no need more . take a look

25. onegirl

ok lol my bad

26. Loser66

|dw:1368223122327:dw|

27. Loser66

calculate it and tell me the answer

28. Loser66

|dw:1368223207231:dw|

29. onegirl

umm 5?

30. Loser66

perfect! now replace

31. Loser66

|dw:1368223296128:dw|

32. onegirl

ok

33. Loser66

you go girl!!! can step up from here?

34. onegirl

so now i find the integral or?

35. Loser66

am I rude when saying that? sorry if you feel so, or I take it back?

36. onegirl

noo is that a sqrt sign?

37. Loser66

yep, from the beginning until now, we don't "substitute " that sqrt, so it's there still

38. onegirl

okay

39. Loser66

so, what's the answer?

40. onegirl

so i got (2 u^(3/2))/3+C

41. Loser66

something wrong there, 1st you forgot 1/2 from du, and it cancel out with your 2/3 to get 1/3 only 2nd, it has a limits so, you have to replace those limit where you have u.

42. Loser66

|dw:1368223960531:dw|

43. Loser66

|dw:1368224029766:dw| that's the final one

44. onegirl

ohhh okay

45. Loser66

glad to hear that.

46. onegirl

thanks!

47. Loser66

yw

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