okay :) i am answering ur question ..
so u have --
2a-b / (a^2+ ab) - (2b - a ) / (b^2 + ab) + (a - b) /ab
= (2a-b)(b^2 + ab) - (2b -a) ( a^2 + ab) / (a^ + ab)(b^2 +ab) + a-b /ab
on multiplying and simplifying u will get ..just multiply and cancel out the equal and opposite terms!
= a^b + a^3 - b^3 - ab^/ (a^+ab)(b^2 + ab) + a-b /ab
= a^2 ( a+b) - b^2 ( a +b ) / ( a^ +ab )(b^2 + ab) + a-b/ab
= (a^2- b^2 ) (a+b) / a(a+b) b (a+b) + a-b/ab
= (a-b)(a+b).(a+b) / ab(a+b)(a+b) + a-b/ab
as a^2 - b^2 = (a+b)(a-b)
cancel out the common terms ..
= a-b / ab + a-b/ab
= 2(a-b)/ab ANSSSSSS
yay !!!!!! u got that dude!