(3/(x + 1)) - (1/(x - 1)) = 4/(x^2 - 1)
(3(x - 1) / (x + 1)(x - 1)) - ((x + 1) / (x + 1)(x - 1)) = 4 / (x^2 - 1)
((3x - 3) / (x^2 - 1)) - ((x + 1) / (x^2 - 1)) = 4 / (x^2 - 1)
(3x - 3) - (x + 1) = 4
3x - 3 - x - 1 = 4
2x - 4 = 4
2x = 4 + 4
2x = 8
x = 8 / 2
x = 4