Question

What is the factored form of the expression x2 − 81

Answer 1

`\left(x+9\right)\left(x-9\right)`

Explanation:

`x^2 - 81`

factor 81 as 9²

`x^2-9^2`

using formula: a² -b² = (a+b)(a-b)

`\left(x+9\right)\left(x-9\right)`

Answer 2

(x + 9)(x - 9)

Explanation:

Apply the Difference of Two Squares formula: x² - y² = (x + y)(x - y)

Rewrite 81 at 9²

⇒ x² - 81 = x² - 9² = (x + 9)(x - 9)