1. 3/×+1 +3/×-1 2. ×/×+y +y×-y 3. 4a/3×-4/(×-2)

1. 3/(x+1) + 3/(x-1)
= 3(x-1) + 3(x+1) / (x+1)*(x-1)
= 3x-3+3x+3 / x^2-1
= 6x / x^2-1

2. x/(x+y) + y/(x-y)
= x (x-y) + y (x+y) / (x+y)*(x-y)
= x^2-xy+xy+y^2 / (x^2 - y)
= x^2 + y^2 / (x^2 - y)

3. 4a/(3x) - 4/(x-2)
= 4a(x-2) - 4(3x) / (3x)*(x-2)
= 4ax - 8a - 12x / 3x^2 - 6x