2. Give the prime factors of the following:
1. 28
2. 45
3. 54
3. Review:
1: One common factor. a x + a y = a (x + y)
2x + 2y = 2 (x + y)
2: Several grouped common
factor. a x + a y + b x + b y = a(x + y)
+ b(x + y) = (a + b ) (x + y)
4. 3. Difference of two squares
x 2 - y 2 = (x + y)(x - y)
x 2 - 49 = (x + 7)(x - 7)
4: Difference of two squares
(x + y) 2 - z 2 = (x + y + z)(x + y - z)
(2x + 3) 2 - 49 = (2x + 3 + 7)(2x + 3 - 7)
5. 5: Sum of two cubes.
x 3 + y 3 = (x + y)(x 2 - x y + y 2)
x3 + 27 = (x + 3)(x2- 3x + 9)
6: Difference of two cubes.
x 3 - y 3 = (x - y)(x 2 + x y + y 2)
x3 - 125 = (x - 5)(x2 + 5x + 25)
6. 7: Difference of fourth Powers.
x 4 - y 4 = (x 2 - y 2)(x 2 + y 2) =
(x + y)(x - y)(x 2 + y 2)
x 4 - 16 = (x 2 - 4)(x 2 + 4)
(x - 2)(x + 2)(x 2 + 4)
7. 8: Perfect square
x 2 + 2xy + y 2 = (x + y) 2
x 2 + 8x + 16 = (x + 4)
9: Perfect square
x 2 - 2xy + y 2 = (x - y) 2
x 2 - 10x + 25 = (x - 5)