m-0.5m等于多少？当m等于0时m-0.5m=0当m不等于0时m-0.5=0.5m
m-0.5m=1m-0.5m=0.5m，m可取任意数
(1-0.5)*m=0.5m
m-0.5m=1m-0.5m=（1-0.5）m=0.5m
m-0.5m等于0.5m
