1) = a^2-4ab+4a^2+b^2-a^2=5b^2-4ab 2)= 2ab-4a^2+b^2-2ab-a2+2ab-b^2=2ab-5a^2 3)= b^2+4ab+4a^2-b^2+2ab-a^2=6ab+3a^2 4) = -b^2+4ab-4a^2+b^2-a^2=4ab-5a^2