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Math Help - Solving a Quadratic Equation by Factoring Question

  1. #1
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    Question Solving a Quadratic Equation by Factoring Question

    I have the problem (x+2)^3 = x^3+8
    I use the cube formula (x+y)^(3) = x^(3) + 3x^(2)y + 3xy^(2) + y^(3) and get 6x^(2) + 12x = 0 and solve for x and get -2.

    But the book says 0 is also an answer. Can someone please tell me why, and why sometimes 0 is not an answer?

    Thanks.
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  2. #2
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    Quote Originally Posted by dwatkins741 View Post
    I have the problem (x+2)^3 = x^3+8
    I use the cube formula (x+y)^(3) = x^(3) + 3x^(2)y + 3xy^(2) + y^(3) and get 6x^(2) + 12x = 0 and solve for x and get -2.

    But the book says 0 is also an answer. Can someone please tell me why, and why sometimes 0 is not an answer?

    Thanks.
    6x^2 + 12x = 0<br />

    factor ...

    6x(x + 2) = 0

    set each factor equal to 0 ...

    6x = 0

    x+2 = 0
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  3. #3
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    Thumbs up Thanks

    I forgot to factor before setting it equal to zero. Btw, how do you make your math text like that?
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