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Q&A #104

Teachers' Lounge Discussion: Factoring trinomials

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From: Carole <cdelvecchio@semo.edu>
To: Teacher2Teacher Public Discussion
Date: 2005033013:13:53
Subject: Re: Re: trinomials


This trinomial can be factored by grouping.  AC = 1575.  Prime factors
of 1575 are 3*3*5*5*7.  Since we're looking for 2 factors of 1575
which sum to -88, choose -63 (3*3*7) and -25 (5*5).

Rewrite the trinomial as 35x^2 -63x -25x +45

Group the first 2 terms and the last 2 terms and factor a common
factor from each group.

7x(5x - 9) - 5(5x - 9)

Factor the binomial that is common to both terms

(5x - 9)(7x - 5)

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