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9.7 Difference of Two Squares (D.O.T.S)

How do we factor this? What looks different?

x2

- 9

Square each term:

1) 4 2) 3y 3) 4x2

4) 8w4

Take the square root of the following terms:

5) 36x2

6) 9 7) 49w

4 8) 16k

2n

2

Practice: Multiply the following:

9) (x-2)(x+2) 10) (2a+3)(2a-3) 11) (1-2x2)(1+2x

2)

What patterns do you notice? Be specific!

Try it! Let’s go the other direction and factor:

12) x2 – 4 13) 9 – b

2 14) w

2 - 1

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Practice factoring (don’t forget to pull out a GCF if possible):

15) 4x2 – 25 16) 36 – c

2 17) 1 – x

4

18) 5h2 – 45 19) w

4 – 9w

2 20) 49k

2 -81

Take it a step further, solve:

21) t2 – 16 = 0 22) 25 = 9q

2

23) 49y4 – 4y

2 = 0 24) 9x

2 – 12x +4 = 0

Difference of Two Squares (D.O.T.S) To use D.O.T.S. we must have:

1. 2.

General Form: a2 – b2 = ___________