Name: Tommygirl98
Who is asking: Student
Level: Secondary

Ok I have a question about common factoring I'm not to sure if you could help me but it's worth a try here it goes. Ok I have a test on Friday and i'm having trouble understanding how to do it here's an example,

-10 + 2b how do you do it and what do they mean by factor?

Thanks for the help.


Lets look at numbers first. Factors of an integer are other integers, greater than 1, that divide it. For example 2, 3, 4, 6... are factors of 24 since they each divide 24. 5 is not a factor of 24. For a pair of numbers, say 12 and 15, common factors are integers that are factors of both. So for 12 and 20, 2 and 4 are the common factors. (The factors of 12 are 2, 3, 4 and 6 and the factors of 20 are 2, 4, 5 and 10.)
   For algebraic expressions like 2b we say 2 and b are factors. In your algebraic expression above, -10 + 2b, you are looking for common factors of -10 and 2b. Here 2, 5, -2 and -5 are factors of 10 and 2 and b are factors of 2b so 2 is the only common factor. Thus 2 divides -10 and 2 divides 2b and therefore 2 divides -10 + 2b. By finding common factors of -10 and 2b you can write

-10 + 2b
=2(-5) + 2b


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