Kenneth S. answered • 11/08/16
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= (3x+7)(x-4) Don't forget to check by multiplying, using F O I L
Kenneth S.
Of course there's a way, although there's nothing wrong with guess and check. Especially in this case when the coefficient of the variable squared term is 3, a prime number; this tells you that the factored structure has to be
(3x ± something)(x±something else) and furthermore one of those ± must be the + and the other must be the opposite, because the product of the two somethings has to come out negative.
Then it's just a matter of "splitting" the 28 into two factors and doing a quick bit of trying out possibilities. Obviously, 3 times -4 makes -12 and 1 times +7 makes seven, and these two things combine to make the net middle term -5x.
Your teacher should be showing you lots of skills AND INSIGHT into factoring. Maybe Common Core is causing teachers today to be inhibited during lectures.
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11/09/16
Michael O.
11/08/16