x2 - 1 = (x + 1)(x - 1)
This comes from a formula that is called "The Difference of Squares."
The formula says that when you are subtracting two square numbers from each other that they can always be factored as such:
a2 - b2 = (a + b)(a - b)
Another example would be to factor x2 - 9.
We could rewrite x2 - 9 as x2 - 32 which when we compare it to the formula above helps us to see that a=x and b=3. This yields the result:
a2 - b2=(a + b)(a - b)
x2 - 32 = (x + 3)(x - 3)
And just for good measure here is another example :)
Factor the following polynomial expression:
x2 - 64
Step 1: Rewrite it as the difference of two squares: x2 - 82
Step 2: Plug in a=x and b=8 into the formula above to get: (x + 4)(x - 4)
(x - 1)(x + 1)
Factor out the GCF and get X(X2-X+1).
(x-1)(x+2)
(x - 1)(5x + 7)
(x + 6)(x - 6)
(x - 1)(x + 1)
x(x-1)
(x + 1)(x - 8)
4(x - 1)(x + 1)
x^2(1 - x)(1 + x)
(x + 3)(x - 1)(x + 1)
Factor out the GCF and get X(X2-X+1).
(x-1)(x+2)
(x-3)(3x+1)
x^2-x+1 cannot be factorised
(x-1)(x-4)
(x-6)(x-1)