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Math Help - Substitution & Elimination

  1. #1
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    Substitution & Elimination

    I don't know how to substitute or eliminate with squares; please help me.
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  2. #2
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    Quote Originally Posted by megs_world View Post
    I don't know how to substitute or eliminate with squares; please help me.
    From the first equation:

     5x^2 = 49 + 3y^2

    From the second equation:

     4x = 11+2y

    Hence

     (4x^2) = (11+2y)^2

     16x^2 = 121 + 44y + 4y^2

    So we have:

     16x^2 = 121 + 44y + 4y^2

     5x^2 = 49 + 3y^2

    Multiply the top one by 5, and the bottom by 20

     80x^2 = 5(121 + 44y + 4y^2)

     80x^2 = 20(49 + 3y^2)

    Now eliminate.

    Alternatively:

     4x = 11+2y

     x = \frac{11+2y}{4}

     5\bigg( \frac{11+2y}{4}\bigg)^2 = 49 + 3y^2
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