mọi người giúp em với ạ

`[` Bạn tham khảo `]`

`A = [1/[x^2 + 2xy + y^2] - 1/[x^2 - y^2]] : (4xy)/(y^2 - x^2)`

`A = [1/[(x + y)^2] - 1/[(x - y).(x + y)]] : (4xy)/(-(x^2 - y^2))`

`A = [x - y - (x + y)]/[(x - y).(x + y)^2] : (4xy)/[-(x - y).(x  +y)]`

`A = [x - y - x - y]/[(x - y).(x + y)^2] . [-(x - y).(x  +y)]/[4xy]`

`A = [-2y]/[(x - y).(x + y)^2] . [-(x - y).(x  +y)]/[4xy]`

`A = [2y.(x - y).(x + y)]/[4xy.(x - y).(x + y)^2]`

`A = 1/[2x.(x + y)]`

`A=  1/[2x^2 + 2xy]`

Vậy `A=  1/[2x^2 + 2xy]`

`#Eirlys07`