Question

using appropriate identity factorize 4x^2-y^2_9

Answer 1

(4x^2 - y^2)_9

{(2x)^2 - y^2 }_9

{(2x+y)(2x-y)}_9

if _ is used for multiplication

then 

9(2x+y)(2x-y) is the answer

Answer 2

Hope this will help you