a)(a-2y)^2+4y(a-y)=a^2-4ay+4y^2+4ay-4y^2=a^2
b)(2m-3)(2m+3)-(2m-1)^2=4m^2-9-(4m^2-4m+1)=4m^2-9-4m^2+4m-1=4m-10=2(2m-5)
(а-2у)2 +4у(а-у)= а2-4ау+4у2+4ау-4у2=а2
(2m-3)(2m+3)-(2m-1)2= 4m2-9-4m2+4m-1=4m-10
