Given a = 2x + y, B = 2x-y, calculate A2-B2

Given a = 2x + y, B = 2x-y, calculate A2-B2

A2-B2=(2x+y)2-(2x-y)2=(4x2+4xy+y2)-(4x2-4xy+y2)=4x2+4xy+y2-4x2+4xy-y2=8xy.