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Math Help - Solving/Factoring an equation

  1. #1
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    Solving/Factoring an equation

    The answer is letter B but I got letter D for my answer... What did I do wrong?
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  2. #2
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    Re: Solving/Factoring an equation

    Hey asilvester635.

    Hint: ab + ac = a*(b+c).
    Thanks from asilvester635 and topsquark
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  3. #3
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    Re: Solving/Factoring an equation

    Chiro's suggestion for looking for common factors is a good one, but your method is fine as well.

    When you get to \displaystyle \begin{align*} 10y^2 - 13y - 3 \end{align*}, you should note that \displaystyle \begin{align*} 10(-3) = -30 \end{align*}, so the two numbers that multiply to give -30 and add to give -13 are -15 and 2. So you should get

    \displaystyle \begin{align*} 10y^2 - 13y - 3 &= 10y^2 + 2y - 15y - 3 \\ &= 2y \left( 5y + 1 \right) - 3 \left( 5y + 1 \right) \\ &= \left( 5y + 1 \right) \left( 2y - 3 \right) \end{align*}
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