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Homework Help: Crazy Simultaneous Equation ?

  1. Jan 10, 2009 #1
    Crazy Simultaneous Equation ?!?

    1. The problem statement, all variables and given/known data

    Solve for x and y
    1)2x - 3y = 1
    2)x2 - 2xy - 3y2 = -3



    2. Relevant equations



    3. The attempt at a solution
    I substituted the linear equation into the quadratic and got a quadratic with only y in it:
    3.) 15y2 - 2y = 13

    I then substituted the linear into eq3 and got a quadratic with only x in it:
    4.) 5x2 - 6x = 9

    Do I need substitute that linear into these quadratics twice more so I get 2 simultaneous quadratics with only x in them and 2 quadratics with only y in them?

    I've been on this question for about half an hour now but this is a sample question from a test so theres no way I could spend that long on a single question on a test. I must be doing it wrong.
     
    Last edited: Jan 10, 2009
  2. jcsd
  3. Jan 10, 2009 #2
    Re: Crazy Simultaneous Equation ?!?

    where is eqn 3?
    You say it has only y in it why aren't you solving it then?
     
  4. Jan 10, 2009 #3
    Re: Crazy Simultaneous Equation ?!?

    Its a quadratic if has y^2 and y. I'll edit the post and put in all the equations I got
     
  5. Jan 10, 2009 #4

    Delphi51

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    Homework Helper

    Re: Crazy Simultaneous Equation ?!?

    Looks good! The rest is easy - just use one of your techniques for solving a quadratic equation to find the number(s) for y.
     
  6. Jan 10, 2009 #5
    Re: Crazy Simultaneous Equation ?!?

    Ah yea I didn't even think of factorizing or anything like that. Thanks.
     
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