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