Question

x^2-4xy+4y^2-(x-2y)^3

Answer 1

x^2-4xy+4y^2 = (x -2y)^2

x^2-4xy+4y^2-(x-2y)^3 =(x -2y)^2   - (x -2y)^3   = (x -2y)^2      * ( 1 -x+2y)