Question 661795
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Hi, there--

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

{{{(y-9)^2-1}}}

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:
{{{a^2-b^2 = (a+b)*(a-b)}}}

In your problem:
{{{(y-9)^2-1=((y-9)+1)*((y-9)-1)}}}

We can simplify this:
{{{(y-9)^2-1=(y-8)*(y-10)}}}

~Mrs. F.
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