2a^2+2ab
------------------— — 1
a^2+2ab+b^2

(2a²+2ab)/(a²+2ab+b²) - 1 = (2a²+2ab-a²-2ab-b²)/(a+b)²==(a²-b²)/(a+b)²=(a+b)(a-b)/(a+b)(a+b)=(a-b)/(a+b)a≠-b