the sum from 2 to infinity of 2/(n^2 - 1)
so first i factor the denominator
2/((n + 1)(n - 1))
this can expressed with partial fractions
2/((n + 1)(n - 1)) = A/(n + 1) + B/(n - 1)
which can be rearanged to
2 = A(n + 1)(n - 1) + B(n + 1)(n - 1)
now I'm stuck. I have one equation and 2 variables. I know there is something I'm forgetting how to do this.