AB所在的直線方程：
y=3x/(m+3)+(6-m)/(m+3)
AC所在直線方程：
y=-5x/(5-m)+(10-m)/(5-m)
M點(diǎn)的坐標(biāo)M(1,0)
M到AB的距離=|9-m|/√[9+(m+3)^2]
M到AC的距離=|5-m|/√[25+(5-m)^2]
由M到AB的距離大于M到AC的距離可以得到：
|9-m|>|5-m|
m??????BC?е?M(1,0)??S??ABM=S??ACM??S??ABM=AB??M??AB?????,S??ACM=AC??M??AC???????AB??M??AB?????=AC??M??AC???????M??AB?????>M??AC???????AB