Question

Can someone please help me Factor 4x^2 - 81

Answer 1

The answer is (2x-9)(2x+9)

4x^2-81
2^2 x^2-9^2
(2x)^2-9^2
(2x-9)(2x+9)

Answer 2

(2x-9)(2x+9)

Explanation:

This is a difference of squares because it can be written as (2x)^2-9^2

The formula for factoring a difference of squares is a^2-b^2=(a-b)(a+b)

So replace a with 2x and b with 9 giving us

4x^2-81=(2x-9)(2x+9)