How do you factor x to the second minus one?

Answer 1

Note that x² - 1 can be written as:

x² + x - x - 1

Then, factor-by-group the expression to get:

x(x + 1) - (x + 1)

= (x - 1)(x + 1)

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