SOLUTION: I am having difficulty factoring trinomials, could you please help me with this problem? {{{ 16b^2+10b-21 }}} Thanks ahead of time.

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Question 8426: I am having difficulty factoring trinomials, could you please help me with this problem?
+16b%5E2%2B10b-21+
Thanks ahead of time.
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Factor:
16b%5E2%2B10b-21+=+%288b-7%29%282b%2B3%29
How did I arrive at this solution? Trial & error mostly.
I know that I needed the factors of -21.
Well, there aren't that many so I tried:
(-1)(21), (1)(-21), (-3)(7), and (3)(-7)
I also know that I needed the factors of 16b%5E2.
I tried: (16b)(b), (2b)(8b), and (4b)(4b)
So I tried these in various combinations to give the desired middle term of +10b. It didn't take too many tries to get:
%288b-7%29%282b%2B3%29 as the factors of 16b%5E2%2B10b-21