原式=1/(x-3)-1/2(x+3)-x/(x-3)²=[2(x+3)(x-3)-(x-3)²-2x(x+3)]/[2(x+3)(x-3)²]=(2x²-18-x²+6x-9-2x²+6x)/[2(x+3)(x-3)²]=(-x²+12x-27)/[2(x+3)(x-3)²]=-(x-3)(x-9)/[...