Factoring Out the Opposite of the GCF
The GCF, the greatest common factor, for -6x2 - 4x is 2x, but we can factor out
either 2x or its opposite, -2x:
-6x2 - 4x |
= 2x( 3x - 2) |
|
= 2x(3x + 2) |
Example 1
Factoring out the opposite of the GCF
Factor out the GCF, then factor out the opposite of the GCF.
a) 5x - 5y
b) -x2 - 3
c) -x3 + 3x2 - 5x
Solution
a) 5x - 5y |
= 5(x - y) |
Factor out 5. |
|
= -5 (-x + y) |
Factor out -5. |
b) -x2 - 3 |
= 1(-x2 - 3) |
The GCF is 1. |
|
= -1(x2 + 3) |
Factor out 1. |
c) -x3 + 3x2 - 5x |
= x(-x2 + 3x - 5) |
Factor out x. |
|
= -x(x2 - 3x + 5) |
Factor out -x. |
|