Question

Can anyone help me? Factorise: 81m^2-1

Answer 1

81m² - 1 = (9m - 1)(9m + 1)

Explanation:

`81m^2-1=9^2m^2-1^2=(9m)^2-1^2\\\\\text{use}\ a^2-b^2=(a-b)(a+b)\\\\=(9m-1)(9m+1)`

Answer 2

(9m-1)(9m+1)

Explanation:

This is a difference of squares

(9m)^2-1^2

Use a^2-b^2=(a-b)(a+b)

So the answer is (9m-1)(9m+1)