SOLUTION: Factor 3a^2 - 15a - 42

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Question 313668: Factor 3a^2 - 15a - 42
Answer by texttutoring(324) About Me  (Show Source):
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All three of those numbers have 3 as a factor, so factor out the 3:

3(a^2 -5a -14)
Now ask yourself, what two numbers multiply to -14, and have a difference of -5? -7 and 2.

3(a^2 -5a -14)
3(a-7)(a+2)