原式=2(x+3)/[2(x+3)(x-3)]-12/[2(x+3)(x-3)]-(x-1)(x-3)/[2(x+3)(x-3)]=(2x+6-12-x²+4x-3)/[2(x+3)(x-3)]=-(x²-6x+9)/[2(x+3)(x-3)]=-(x-3)²/[2(x+3)(x-3)]=(3-x)/(2x+6)