Hi, there--

Problem: 
Factor this expression using the difference of two squares. Assume that variables represent whole numbers.



Answer:
The difference of two square factoring method is useful when you have one expression 
subtracted from another AND you can write both expressions in the form of something-
squared.

In this case, you subtract 1 from (y-9}^2. Both of these can be written as something-squared:
 1 = 1^2 and (y-9)^2 is already in that form. 

Difference of two squares factors like this:


In your problem:


We can simplify this:


~Mrs. F.