（1）a/（x-a）+b=1
a/（x-a）=1-b
x-a = a/(1-b)
x = a+a/(1-b) = a{(1+1/(1-b)} = a(2-b)/(1-b)
（2）m/x-n/(x+1)=0
m/x=n/(x+1)
[m(x+1)]/[x(x+1)]=(nx)/[x(x+1)]
m(x+1)=nx
mx+m=nx
mx-nx=m
(m-n)x=m
∵m≠n
∴m-n≠0
∴x=m/(m-n)