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Factoring
Posted:
Jan 8, 2012 8:35 PM
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A student asked me how to factor x^3-3x^2-4x+12
So I took a guess (correctly it seems) that since 12 factors as 2,2,3 one of
the factors was likely to be x-2. Dividing by x-2 gives x^2-x-6 which is
easy to factor into (x-3)(x+2) so the answer is (x-2)(x-3)(x+2).
Is there a way to do that whithout guesswork?
Suppose I had a more complicated example such as (2x+1)(3x-2)(4x+5) I
haven't multiplied it out but how would I find the factors if I didn't know
them in advance?
Thanks for any enlightenment.
old guy
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