A binomial of difference of two squares has a form:
`a^2 - b^2`
From its name difference of two squares, the operation between the two terms a^2 and b^2 is subtraction.
And its factor form is:
`a^2 - b^2=(a-b)(a+b)`
`x^2 - 9`
This is a binomial of difference of two squares because:
(1) the first term is in the form a^2,
(2) the second term can be express as b^2, since 9=3^2, and
(3) the operation between the two terms is subtraction.
So, the given binomial can be re-written as:
Now that it is the form a^2 - b^2, apply its factor (a-b)(a+b).