原式
=(x+3)(x-1)/(x+3)(x-3) *(x-2)(x-3)/(x+1)(x-1)
=(x-1)/(x-3) *(x-2)(x-3)/(x+1)(x-1)
=(x-1)/(x-3) *(x-2)(x-3)/(x+1)(x-1)
=(x-2)/(x+1)
取x=1,则
原式=-1/2