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