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Math Help - completing the square

  1. #1
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    Post completing the square

    Complete the square:
    2x^2+8x+1
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  2. #2
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    Re: completing the square

    Quote Originally Posted by Khevish View Post
    Complete the square:
    2x^2+8x+1
    2x^2 + 8x + 1

    2(x^2 + 4x) + 1

    2(x^2 + 4x + 4) + 1 - 8

    finish it ...
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  3. #3
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    Re: completing the square

    how do you get -8? ^^
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  4. #4
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    Re: completing the square

    Maybe it would help if it was written like this

    \displaystyle \begin{align*} 2(x^2 + 4x) + 1 &= 2(x^2 + 4x + 2^2 - 2^2) + 1 \\ &= 2(x^2 + 4x + 4 - 4) + 1 \\ &= 2(x^2 + 4x + 4) + 2(-4) + 1 \\ &= 2(x^2 + 4x + 4) - 8 + 1 \end{align*}
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