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Math Help - solve the equation by an appropriate substitution

  1. #1
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    solve the equation by an appropriate substitution

    solve the equation by making an appropriate substitution

    x^4 - 5x^2 + 4 = 0

    any help in explaining what needs to be done to solve this question will be appreciated. what substitution are they talking about to be more precise on whats confusing me about this question. (should i just substitute random values for x until i find a solution?)
    Last edited by netlab; January 12th 2009 at 03:40 PM.
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  2. #2
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    Quote Originally Posted by netlab View Post
    solve the equation by making an appropriate substitution

    x^4 - 5x^2 + 4 = 0

    any help in explaining what needs to be done to solve this question will be appreciated. what substitution are they talking about to be more precise on whats confusing me about this question. (should i just substitute random values for x until i find a solution?)
    If you let  y = x^2 , then the equation becomes:

     y^2 - 5y + 4 =0

    Which is a quadratic. Can you solve those?
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  3. #3
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    ok thanks a lot that clears up a lot, and yes i can solve quadratic equations
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  4. #4
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    Quote Originally Posted by netlab View Post
    ok thanks a lot that clears up a lot, and yes i can solve quadratic equations
    No problem.

    Just remember that once you have solved for y, you must change the variable back to the original and solve for x!
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