原式=2(x-3)/(x-2)²*1/(x+3)*[-(x+3)(x-2)/(x-3)]
=-2(x-3)/(x-2)²*1/(x+3)*(x+3)(x-2)/(x-3)
=-2(x-3)/(x-2)²*(x-2)/(x-3)
=-2/(x-2)