1) Сокращение в основном :
5b/a-x*a*x/10b =>
5b*1/a-x*a*x/5b*2 =>1/a-x*a*x/2=>ax/2(a-x)
2) 2x^2/a-b
------------ =
6x^2/a-b
(2x^2/a-b)(a-b/6x^2)=>(1/a-b)(a-b/3)=>(1/1)(1/3)=>1/3
3)xy+y^2/a+b
--------------- =
x^2-y^2/a+b
(xy+y^2/a+b)(a+b/x^2-y^2)=>(xy+y^2/1)(1/x^2+y^2)=>y(x+y)/(x+y)(x-y)=>y/x-y