Question

`81x^(2) -1` using furmulae (a-b)(a+b)

Answer 1

Hello!

Answer:

`\Large \boxed{\sf (9x - 1)(9x+1)}`

Explanation:

We want to factorize this expression:

`\sf 81x^2 - 1`

We have this formula:

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

Apply the formula:

`\sf a =9x\\b = 1`

`\sf 81x^2 - 1 \\\\= (9x)^2 - 1^2 \\\\ \boxed{\sf= (9x - 1)(9x+1)}`

Answer 2

(9x - 1)(9x + 1)

Explanation:

81x² - 1 ← is a difference of squares and factors in general as

a² - b² = (a - b)(a + b)

given

81x² - 1 , that is

(9x)² - 1² ← with a = 9x and b = 1 , then

= (9x - 1)(9x + 1) ← in factored form