Question

factor if possible:
4-81(x+y)^2

Answer 1

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

Answer 2

4-81(x+y)^2

use formula a^2-b^2=(a-b)(a+b)

(2)^2 - (9(x+y))^2
=(2+9(x+y))(2-9(x+y))