1.(x-2)(x+2)-(x+1)(x-3) =(x^2-4)-(x^2-2x-3) =2x-12.(ab+1)^2-(ab-1)^2 =(ab+1+ab-1)(ab+1-ab+1) =2ab3.(2x-y)^2-4(x-y)(x+2y)=(4x^2-4xy+y^2)-(4x^2+4xy-8y^2) =9y^2-8xy