5.5 Factoring Special Patterns 12/12/12
Perfect Squares
Review Find the product (use FOIL) 1.(x + 2) (x – 2) Answer: x 2 – 4 2. (x + 5) (x – 5) Answer: x 2 – (2x – 3) (2x + 3) Answer: 4x 2 – 9 What’s the pattern???
Difference of Two Squares Pattern (a + b) (a – b) = a 2 – b 2 In reverse, a 2 – b 2 gives you (a + b) (a – b) Examples: 1. x 2 – 4 = x 2 – 2 2 = (x + 2) (x – 2) 2. x 2 – 144 =(x + 12) (x – 12) 3. 4x 2 – 25 = (2x + 5) (2x – 5)
If you can’t remember that, you can still use the big X method. Ex. x 2 – Think of 2 numbers that Multiply to -4 and Add to 0 2 x -2 = = Answer: (x + 2) (x - 2) Ex. x 2 + 0x – 4
Ex. x 2 – Think of 2 numbers that Multiply to -144 and Add to 0 12 x -12 = = Answer: (x + 12) (x - 12) x 2 + 0x – 144
4(-25) = Think of 2 numbers that Multiply to -100 and Add to x 10 = = Answer: (2x - 5) (2x + 5) Factor: 4x Simplify like a fraction. ÷ by Simplify like a fraction. ÷ by 2 4x 2 + 0x - 25
Homework WS