(x-1)/(x-2)=m/(x-1)+1
两边同时乘以(x-2)(x-1).得,
(x-1)^2=m(x-2)+(x-1)(x-2)
整理：
x^2-2x+1=mx-2m+x^2-3x+2
即（1-m）x=1-2m
若方程无解,则1-m=0.
解得m=1