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May 28, 2016
Posted by **Gretchen** on Thursday, June 4, 2009 at 12:59am.

I need help trying to figure out how to factor each quantity or parentheses.

and then simplifying it.

- 8th Grade Algebra -
**MathMate**, Thursday, June 4, 2009 at 1:07amFor (b^2-10b+21), start with listing the factors that multiply to give 21.

1,21

3,7

7,3

21,1

As 21 is positive and -10b is negative, you will find that the factors are in the following form:

(b-x)(b-y)

where x and y are chosen from the pair of factors. If you multiply out the factors, you will get

(b-x)(b-y)=b^2-(x+y)b+xy

Thus, you will choose from the list of factors a pair which will give

xy=21 and x+y=10.

Try the same for the denominator. It has more factors, so the list of factors will look like:

1,28

2,14

4,7

7,4

14,2

28,1

The method to follow is exactly the same as the numerator.

Tell us what you found.