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Math Help - Solving Quadratic Equations by the Quadratic Formula

  1. #1
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    Solving Quadratic Equations by the Quadratic Formula

    Hey Guys,
    I am a bit confused on what to do for this problem. If I can get some help I'd appreciate it.

    Suppose that f(x) = x4 + 7x2+ 12. Find the values of x such that

    a. f(x) = 12
    b. f(x) = 6

    I figured part b already but I am having trouble on part (a) which is

    12 = x4 + 7x2+ 12
    -12 -12

    Now I'm left with x4 + 7x2

    I use "Let u = x2 , Let u2 = x4"

    u2 + u


    Do I get a third term by completing the square method? I am lost with this step.
    Last edited by Cake; May 7th 2013 at 12:27 AM.
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  2. #2
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    Re: Solving Quadratic Equations by the Quadratic Formula

    It is not must that quadratic polynomial should always have three terms. It may be a monomial / binomial or a trinomial.
    Now you have u(u+ 7u ) = 0
    In second case we will have
    u^2 + 7u + 6 = 0
    Thanks from Cake
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  3. #3
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    Re: Solving Quadratic Equations by the Quadratic Formula

    What is the quadratic formula? What are the values of a, b, and c?
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    Re: Solving Quadratic Equations by the Quadratic Formula

    Quote Originally Posted by ibdutt View Post
    It is not must that quadratic polynomial should always have three terms. It may be a monomial / binomial or a trinomial.
    Now you have u(u+ 7u ) = 0
    In second case we will have
    u^2 + 7u + 6 = 0

    Hey ibdutt,

    You are correct
    Honestly, I did factor the problem and ended up with u(u + 7u) = 0 but I thought it looked wrong and I wasn't used to seeing a quadratic polynomial with two terms. Thanks for clearing things up for me!

    Cheers!
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    Re: Solving Quadratic Equations by the Quadratic Formula

    Quote Originally Posted by mathguy25 View Post
    What is the quadratic formula? What are the values of a, b, and c?
    As ibdutt mentioned "It is not must that quadratic polynomial should always have three terms. It may be a monomial / binomial or a trinomial."
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