Factoring using Difference of Squares

Contributed by:
NEO
This pdf includes the following topics:-
Factoring Chart
Determine the pattern
Difference of Squares
4 Steps for factoring Difference of Squares
1. Notes 8.5
Factoring using
difference of squares.
2. Factoring Chart
This chart will help you to determine
which method of factoring to use.
Type Number of Terms
1. GCF 2 or more
2. Difference of Squares 2
3. Determine the pattern
1 = 12 These are perfect squares!
4 = 22 You should be able to list
9 = 32 the first 15 perfect
16 = 42 squares in 30 seconds…
25 = 52
Perfect squares
36 = 62 1, 4, 9, 16, 25, 36, 49, 64, 81,
… 100, 121, 144, 169, 196, 225
4. Review: Multiply (x – 2)(x + 2)
Notice the
First terms: x2 middle terms
eliminate
x -2
Outer terms: +2x each other!
Inner terms: -2x
Last terms: -4
x x2 -2x
Combine like terms.
x2 – 4 +2 +2x -4
This is called the difference of squares.
5. Difference of Squares
2 2
a - b = (a - b)(a + b)
or
2 2
a - b = (a + b)(a - b)
The order does not matter!!
6. 4 Steps for factoring
Difference of Squares
1. Are there only 2 terms?
2. Is the first term a perfect square?
3. Is the last term a perfect square?
4. Is there subtraction (difference) in the
problem?
If all of these are true, you can factor
using this method!!!
7. 1. Factor x2 - 25
When factoring, use your factoring table.
Do you have a GCF? No
Are the Difference of Squares steps true?
Two terms? Yes x2 – 25
1st term a perfect square? Yes
2nd term a perfect square? Yes
Subtraction? Yes ( x + 5 )(x - 5 )
Write your answer!
8. 2. Factor 16x2 - 9
When factoring, use your factoring table.
Do you have a GCF? No
Are the Difference of Squares steps true?
Two terms? Yes 16x2 – 9
1st term a perfect square? Yes
2nd term a perfect square? Yes
Subtraction? Yes (4x + 3 )(4x - 3 )
Write your answer!
9. 3. Factor 81a2 – 49b2
When factoring, use your factoring table.
Do you have a GCF? No
Are the Difference of Squares steps true?
Two terms? Yes 81a2 – 49b2
1st term a perfect square? Yes
2nd term a perfect square? Yes
Subtraction? Yes (9a + 7b)(9a - 7b)
Write your answer!
10. Factor x 2 – y 2
1. (x + y)(x + y)
2. (x – y)(x + y)
3. (x + y)(x – y)
4. (x – y)(x – y)
Remember, the order doesn’t matter!
11. 4. Factor 75x2 – 12
When factoring, use your factoring table.
Do you have a GCF? Yes! GCF = 3
3(25x2 – 4)
Are the Difference of Squares steps true?
Two terms? Yes 3(25x2 – 4)
1st term a perfect square? Yes
2nd term a perfect square? Yes
Subtraction? Yes
Write your answer! 3(5x + 2 )(5x - 2 )
12. Factor 18c 2 + 8d 2
1. prime
2. 2(9c2 + 4d2)
3. 2(3c – 2d)(3c + 2d)
4. 2(3c + 2d)(3c + 2d)
You cannot factor using
difference of squares
because there is no
subtraction!
13. Factor -64 + 4m2
1. prime
2. (2m – 8)(2m + 8)
3. 4(-16 + m2)
4. 4(m – 4)(m + 4)
Rewrite the problem as
4m2 – 64 so the
subtraction is in the
middle!