SOLUTION: Well, in class, we were doing Factoring by grouping. I really hope you know what that means, because I'm having a hard time typing up an example problem. So I'll just leave it up t

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Question 34805: Well, in class, we were doing Factoring by grouping. I really hope you know what that means, because I'm having a hard time typing up an example problem. So I'll just leave it up to you.
ab + 7b - 3a-21

Thank you in advance =)
Answer by longjonsilver(2297) (Show Source):
You can put this solution on YOUR website!
Typically, if the question asks you to factorise by grouping, then it will be possible to do it... that is the first thing to remember :-)

ab + 7b - 3a - 21 --> typical set of terms: all different and what the hell are the factors? etc

well pick 2 terms that you can factorise:
how about ab and 7b? --> b(a+7)
and also -3a - 21 --> -3(a+7)
Voila...a like term, so:

ab + 7b - 3a - 21
b(a+7) -3(a+7)

Now we have 2 terms both of which have a (a+7) which can be factored out, leaving:
(a+7)(b-3)

jon.