1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Solve the system x+y=9, x^2 - y^2 = 36 for x and y

  1. Sep 12, 2005 #1
    Hi, i just sat my maths exam, and i had a very strange question.... i dont know how to do it...

    x+y=8
    x^2-y^2=36

    find the values for x and y

    Thanks
     
  2. jcsd
  3. Sep 12, 2005 #2
    y = 8-x

    x^2 - (8-x)^2 = 36

    x^2 - (64-16x+x^2) = 36

    16x - 64 = 36
     
  4. Sep 12, 2005 #3
    is that it?

    i did y^2-x^2=36
    (x-y)(x+y)=36
    (x-y)(8)=36
    x-y=36/8

    is any of that correct?
     
  5. Sep 13, 2005 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    According to Whozum, 16x- 64= 36 so x= 100/16= 25/4= 6.25 and y= 8- 6.25= 1.75.

    x-y= 6.25- 1.75= 4.5 and 36/8= 9/2= 4.5.

    Your statement is correct but is not a solution to the "problem" which, I suppose, was to solve the two equations.

    In fact, the only thing strange I see about your "question" is that there was no "question"! Are you sure you didn't leave something out- like "solve this pair of equations" or "what are x and y"?
     
  6. Sep 13, 2005 #5

    VietDao29

    User Avatar
    Homework Helper

    Yup. This is correct. Since you have 2 unknowns, you need 2 equations. And you have already had 2 equations. You can then solve:
    [tex]\left\{ \begin{array}{l}x + y = 8 \\ x - y = \frac{9}{2} \end{array} \right.[/tex]
    for x, and y.
    Viet Dao,
     
  7. Sep 13, 2005 #6
    Me or him?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Solve the system x+y=9, x^2 - y^2 = 36 for x and y
Loading...