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