factor x^2 - 1

Question

This is one of my homework questions, I understand factoring but I don't understand this one.

Answer 1

If you know how to factor you can write this as 

 

x^2 + 0x - 1

 

and now factor as usual.  You will be looking for 2 numbers that add to 0 and multiply to -1.  

 

By the way, this problem is a special kind of factoring called a difference of squares.  

 

When you have something of the form x^2 - a^2 it will always factor as (x-a)(x+a)

 

Answer 2

x²-1 is the difference of two squares

(a²-b²)=(a-b)(a+b) is the general form

(x²-1)=(x-1)(x+1)