1. Factoring Difference of Two Squares

2. What Numbers are Perfect Squares?
List the first 20 Perfect Squares 1 4 9 16 25 36 49 64 81
100
121
144
169
196
225
256
289
324
361
400

3. Factoring: Difference of Two Squares
Count the number of terms. Is it a binomial?
Is the first term a perfect square?
Is the last term a perfect square?
Is it, or could it be, a subtraction of two perfect squares?
x2 – 9 = (x + 3)(x – 3)
The sum of squares will not factor a2 + b2

4. Using FOIL we find the product of two binomials.

5. Rewrite the polynomial as the product of a sum and a difference.

6. Conditions for Difference of Squares
Must be a binomial with subtraction.
First term must be a perfect square.
(x)(x) = x2
Second term must be a perfect square (6)(6) = 36

7. Check for GCF.
Sometimes it is necessary to remove the GCF before it can be factored more completely.

8. Removing a GCF of -1.
In some cases removing a GCF of negative one will result in the difference of squares.
Alternate Method
Now you can use algebra to show that they are equivalent

9. Difference of Two Squares
You Try

11. Factoring - Difference of Squares