## anonymous 4 years ago Solve the following system. 4x^2 + 9y^2 =72 x^2 - y^2 = 5 The solutions are?

1. anonymous

i've tried to do this at least 5 times. i don't understand it at all

2. mathslover

|dw:1337656235090:dw|

3. mathslover

|dw:1337656263685:dw|

4. mathslover

|dw:1337656308816:dw|

5. anonymous

or multiply the second equation by -4

6. mathslover

|dw:1337656338440:dw|

7. mathslover

|dw:1337656365038:dw|

8. mathslover

|dw:1337656398578:dw|

9. anonymous

$4x^2+9y^2=72$ $-4(x^2-y^2)=-4(5)$

10. mathslover

|dw:1337656433069:dw|

11. anonymous

there's supposed to be 2 solutions: The solutions are: (_,_) & (_,_)

12. anonymous

$4x^2+9y^2=72$ $-4x^2+4y^2=-20$ add them together to get $13y^2=52$

13. anonymous

trust me, i've gotten all the solutions possible. but the answer is still wrong.

14. anonymous

$y^2=\sqrt{\frac{52}{13}}$

15. mathslover

the solutions are : sqrt(52/11) and sqrt(107/11)

16. anonymous

but there's 4 solutions.

17. mathslover

@ outkast i think y = sqrt(52/11) u wrote y^2 = sqrt(52/13) ?

18. anonymous

yeah i think there might be aproblem with your's mine is correct i thinkkk let me check

19. anonymous

yeah mine is correct .. by elimination

20. mathslover

u can write it as : |dw:1337656633671:dw|

$y=\pm2$$x=\pm3$

22. anonymous

i also got that ^

23. anonymous

i'ma cheat *grabs calculator

24. anonymous

lol, i've done that too! ^

25. anonymous

ahh wait mathslover you have 7 instead of 9

26. mathslover

hey sorry , i took 4x^2 + 7y^2 but it is 4x^2 + 9y^2 , therefore the 4 solutions are : |dw:1337656820684:dw|

27. anonymous

i believe you made a 9 really badly and thought it was a 7 the first equation is 4x^2+9y^2=72

28. anonymous

For y, I got y= +/- sqrt (52/13)

29. anonymous

thats right now for x

30. mathslover

yes sorry , y = + 2 , -2 x = +3 , -3

31. mathslover

@Outkast3r09 x = +3 , -3 right ?

32. anonymous

$x^2-(2^2)=5$ $x^2-(-2^2)=5$

33. anonymous

x = +/- 3

34. anonymous

$x^2-4=5$ $x^2-4=5$

$\sqrt{52/13}=\pm2$$x ^{2}=9$$x=\pm3$

36. anonymous

I was slow, I was using a crappy calculator.

37. anonymous

does this mean it's a multiplicity of 2?

38. anonymous

@thejoshfish did you try putting in y= +/- sqrt (52/13) and x=+/- 3?

39. anonymous

@Outkast3r09 it means 3*3 and (-3)(-3).

40. anonymous

i sure did. haha trust me, i tried everything. i'm so fed up. but you guys are wonderful.

41. anonymous

42. anonymous

owl?

43. anonymous

Talk with your instructor. I'm taking statics and have the instructor's manual. They're wrong way more times than I'd like them to be. I think the grad students who write the manuals aren't getting enough sleep.

44. anonymous

Online web learning

45. anonymous

what does it say the answers are josh?

46. anonymous

47. anonymous

it doesn't tell me. but thanks for helping.

48. anonymous

sometimes those sites have like a function button with like +- and what not . that could be the problem or try 3,-3 , -2 ,2

49. anonymous

If you have to take the higher level physics series, they might make you use MasteringPhysics. Have fun with that! Groans.