(3d+1)/(2d+2)-1=[3d+1-2d-2]/(2d+2)=[d-1]/2(d+1)
[d-1]/2(d+1)*(d+1)/6(d-1)=1/12
6x+1 6x-1 6x²+19x+3+6x²-19x +3 12x²+6
------ + -------- = ----------------------------------- = ---------------------
x-3 x+3 x²-9 x²-9
6(2x²+1) x²-9
------------ * --------------- = 6
x²-9 2x²+1