(a-2)分之a-(a²-2a)分之2a-a分之2
=[a(a-2)]分之a²-[a(a-2)]分之(2a)-[a(a-2)]分之[2(a-2)]
=[a(a-2)]分之[a²-2a-2(a-2)]
=[a(a-2)]分之(a²-4a+4)
=[a(a-2)]分之(a-2)²
=a分之(a-2)
=1-a分之2
=1-(2分之3)分之2
=1-3分之4
=-3分之1