Tính

a.x+2/x-2-2/x(x-2) = 1/x
b.x/2(x-3)+x/2x+2=2x/(x+1)(x-3)
c.1/7-x = x-8/x-7 - 8
d.1/x+1 - 5/x-2 = 15/(x+1)(2-x)