81y4 - 16

i know its A2 – b2 = (a-b)(a+b) but i cant figure it out

helpppppppp

When writing online, x^2 = x squared.

(9y^2 - 4)(9y^2 + 4) = (3y - 2)(3y + 2)(9y^2 + 4)

To solve the expression 81y^4 - 16, you correctly recognized it as a difference of squares. The formula you mentioned, A^2 - B^2 = (A - B)(A + B), is precisely what we need to use.

In this case, let's consider 81y^4 as A^2 and 16 as B^2. Now we can rewrite the expression as (81y^2)^2 - 4^2.

Now applying the formula, we have:

(81y^2 - 4)(81y^2 + 4)

So, the solution is (81y^2 - 4)(81y^2 + 4).