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Math Help - need help with factoring

  1. #1
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    need help with factoring

    Can someone please explain to me how to do this problem. Thank You.


    2x^2-3x-5=0
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by hmonaghan09 View Post
    Can someone please explain to me how to do this problem. Thank You.


    2x^2-3x-5=0
    the numbers here are easy enough to do trial and error with. you should have (2x + a)(x + b) = 0

    now, you want a and b such that a*b = -5 and a + 2b = -3


    or if trial and error isn't your thing. try the ac method.

    multiply the a and c terms, that is the 2x^2 and the -5, you get -10x^2

    now you want two numbers that when you multiply them you get -10x^2 and when you add them you get the middle term ( -3x). note that -5x and +2x works.

    split the middle term into these two numbers, you get

    2x^2 + 2x - 5x - 5 = 0

    factor the left side by grouping, you get

    2x(x + 1) - 5(x + 1) = 0

    \Rightarrow (x + 1)(2x - 5) = 0

    now continue using the zero-factor property
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