1) 2a/2a+b - 4a²/(2a+b)² = 2a(2a+b)-4a²/(2a+b)² = 4a²+2ab-4a²/(2a+b)²=
=2ab/(2a+b)²
2)2a/(2a-b)(2a+b) -1/2a-b = 2a-2a-b/(2a-b)(2a+b) = -b/(2a-b)(2a+b)
3) 2ab/(2a+b)² * (2a-b)(2a+b)/(-b)= -2a(2a-b)/2a+b
4) -2a(2a-b)/2a+b * b+2a/2a(b-2a)=2a(b-2a)/2a+b * b+2a/2a(b-2a) =
=1