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Math Help - Quadratic Equations and Substituting "Appropriately?"

  1. #1
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    Quadratic Equations and Substituting "Appropriately?"

    I have a section in my book that is asking me to "make an appropriate substitution" for a set of problems; and the book doesn't even give examples on how to do this sort of thing.

    Here is one for example:

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

    Help, anyone?

    Thanks
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  2. #2
    Super Member Quacky's Avatar
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    Re: Quadratic Equations and Substituting "Appropriately?"

    Let x^2=k
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    Super Member TheChaz's Avatar
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    Re: Quadratic Equations and Substituting "Appropriately?"

    Quote Originally Posted by annon25 View Post
    I have a section in my book that is asking me to "make an appropriate substitution" for a set of problems; and the book doesn't even give examples on how to do this sort of thing.

    Here is one for example:

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

    Help, anyone?

    Thanks
    They want you to make a substitution (let's use "k", as Quacky suggests) so that your equation can be written as
    ak^2 + bk + c = 0.

    With k = x^2, we have
    k^2 - 5k + 4 = 0
    (k .... )(k ....) = 0
    etc.
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