(x-3)分之1-（6+2x）分之1-x
=1/(x-3) + (x-1)/2(x+3)
=[2(x+3)+(x-1)(x-3)]/[2(x+3)(x-3)
=(2x+6+x²-4x+3)/[2(x+3)(x-3)]
=(x²-2x+9)/(2x²-18)