Question

What are the zeros of `x^2-9` ?

Answer 1

`x=3` and `x=-3`

Explanation:

The difference of squares identity can be written:

`a^2-b^2=(a-b)(a+b)`

Note that both `x^2` and `9=3^2` are perfect squares, so we find:

`x^2-9 = x^2-3^2 = (x-3)(x+3)`

So the zeros are `3` and `-3`