(x-c)/(b-x)=c/d
d(x-c)=c(b-x)
dx-dc=cb-cx
(c+d)x=c(b+d)
1.
当c+d=0时,
c(b+d)=0
b=c=-d,
方程的解为x≠b;
2.
当c+d≠0时,
x=c(b+d)/(c+d).