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Homework Help: Solving nonlinear systems.

  1. May 14, 2008 #1
    1. The problem statement, all variables and given/known data

    Solve the nonlinear system.

    x^2-2y^2=16
    x^2+y^2=25

    2. Relevant equations

    n/a?

    3. The attempt at a solution

    ive tried subtracting 1 equation from the other...
    (x^2-2y^2+9)=25
    -(x^2+y^2)=25
    -3y^2+9=25
    -3y^2=16
    y^2=-16/3
    y=root of -16/3...
    im not even sure if that part is right, also, i dont know where to go after that.
    help?
     
  2. jcsd
  3. May 14, 2008 #2
    You've forgotten to subtract the RHS as well.
     
  4. May 14, 2008 #3
    huh? im confused? what is the RHS? i really am confused on where to start in general.
     
    Last edited: May 14, 2008
  5. May 14, 2008 #4
    When you subtracted one equation from the other, you subtracted the left-hand side (LHS) of your equations, but did not do the same for the right-hand side (RHS), which was 25-25 = 0.
     
  6. May 14, 2008 #5
    okay...
    (x^2-2y^2+9)=25
    -(x^2+y^2)=25
    -3y^2+9=0
    -3y^2=-9
    y^2=-3
    y=null?
     
  7. May 14, 2008 #6

    Dick

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    Science Advisor
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    You have -3y^2=(-9). That doesn't give you y^2=(-3), does it? I think I remember once dividing -9 by -3 and I didn't get -3.
     
  8. May 14, 2008 #7
    awesome. figured it out. thanks for all the help people :)
     
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