Question

How do you factor `49a^2 - 81b^2`?

Answer 1

You may notice that `49=7^2and81=9^2` are both squares.

Explanation:

So `49a^2=(7a)^2and81b^2=(9b)^2` are also squares, and then we can use the special product of the form: `x^2-y^2=(x+y)(x-y)`

`=(7a+9b)(7a-9b)`