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Math Help - factorise

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    factorise

    can 3x^2+2x-5 be factorised?
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    Quote Originally Posted by decoy808 View Post
    can 3x^2+2x-5 be factorised?
    is b^2-4ac a perfect square number?

    if yes, then the quadratic is factorable.

    if not, then no.
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    (x-1)(3x+5)
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    Quote Originally Posted by Raoh View Post
    (x-1)(3x+5)
    Because  b^2-4ac is a perfect square.( \Delta =64 )
    if b^2-4ac was negative or not a perfect square we wouldn't be able to factorize.(as Skeeter said )
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    Quote Originally Posted by decoy808 View Post
    can 3x^2+2x-5 be factorised?
    split coefficient of x^2, ie. 3, into its factors 3x and 1x. also split the constant -5 into -1 and +5
    you will find that:
    3 x -1 = -3
    1 x +5 = +5
    putting these two products together you have (-3) + (+5) = (+2), which is the coefficient of x. however when you fill up the brackets with these factors you don't write (3x - 1)(x + 5). You write (3x + 5)(x - 1).
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