How do you factorise x squared minus 1?

Answer 1

x2-1=(x-1)(x+1)

It factors out like this because it's the difference of two squares. It only works with subtraction and is always in the format with two groups of parenthases. For example: 16x-4. 16 and 4 are both squares, so it factors out like this: (4x+2)(4x-2). One set is always minus, the other is always plus. The order doesn't matter.