Question

Factor the polynomial: x^2-81

Answer 1

It's a difference of squares:
\[a^2-b^2 = (a+b)·(a-b)\]
x^2 is the square of what? 81 is the square of what?

Answer 2

so , it will be (x+9)(x-9)?

Answer 3

Exactly, you can check the result by doing the multiplication