原式=(x-2)/2(x-3)÷[-5/(x-3)-(x+3)]
=(x-2)/2(x-3)÷[-5-(x²-9)]/(x-3)
=(x-2)/2(x-3)·(x-3)/[-(x+2)(x-2)]
=-1/2(x+2)
=-1/(2x+4)