(x-y)2+x(y-x) = x^2 - 2xy + y^2 + xy - x^2 = y^2 - xy
(a+b)2 - 2b(a-b) = a^2 + 2ab + b^2 - 2ab + 2b^2 = a^2 + b^2 + 2b^2 = a^2 + 3b^2
-5(1-2c)2 = -5(1 - 4c + 4c^2) = -5 + 20c - 20c^2
-4(3m+n)2 = -4(9m^2 + 6mn + n^2) = -36m^2 - 24mn - 4n^2
Proof: a(a+b) + b(a+b) = a^2 + ab + ab + b^2 = a^2 + 2ab + b^2 = (a+b)^2
Proof: (a-b)2 = a(a-b) - b(a-b) = a^2 - ab - ab + b^2 = a^2 - 2ab + b^2 = (a-b)^2
(x-y)2+x(y-x) = x^2 - 2xy + y^2 + xy - x^2 = y^2 - xy
(a+b)2 - 2b(a-b) = a^2 + 2ab + b^2 - 2ab + 2b^2 = a^2 + b^2 + 2b^2 = a^2 + 3b^2
-5(1-2c)2 = -5(1 - 4c + 4c^2) = -5 + 20c - 20c^2
-4(3m+n)2 = -4(9m^2 + 6mn + n^2) = -36m^2 - 24mn - 4n^2
Proof: a(a+b) + b(a+b) = a^2 + ab + ab + b^2 = a^2 + 2ab + b^2 = (a+b)^2
Proof: (a-b)2 = a(a-b) - b(a-b) = a^2 - ab - ab + b^2 = a^2 - 2ab + b^2 = (a-b)^2