I was aked to prove that (a - b)^2 = (a + b)^2 - 4ab

Answer 1

LS = (a-b)^2
= a^2 - 2ab + b^2

RS = (a+b)^2 - 4ab
= a^2 + 2ab + b^2 - 4ab
= a^2 - 2ab + b^2
= LS

Q.E.D.
or
(quid est demonstrata)
(Thus it has been proven)