what's the error in nonlinear solution code?

 In false position method

-
fx=inline('exp(-2*x)-0.5')
a=input('a=');<<0
b=input('b=');<<1
fa=fx(a);
fb=fx(b);
if fa*fb>0.0
 fprintf('not value in rangement');
 return
 elseif fa==0.0
 fprintf('a is true value');
 return
 elseif fb==0.0
 fprintf('b is true value');
 return
 end
epsilon=0.0001;
imax=1000;
for iter=1:imax
   xc=b-fb*(a-b)/(fa-fb);
   fc=fx(xc);
   fprintf('\n xc f(xc) : %f , %f', 'xc', 'fc');
   if abs(fc) <= epsilon
      fprintf('\n value xc= %f','xc');
      return
   end
 test = fa*fc;
 if test <0.0
    b=xc;
    fb=fc;
 elseif test > 0.0
    a=xc;
    fa=fc;
 end
end

 xc f(xc) : 120.000000 , 99.000000
 xc f(xc) : 102.000000 , 99.000000
 xc f(xc) : 120.000000 , 99.000000
 xc f(xc) : 102.000000 , 99.000000
 value xc= 120.000000
 value xc= 99.000000>>

i don't understand why the result show '120' repeatedly. which means what??

thanks for you help