clc
f1=@(x) exp(-x)-x;

function yy=secante(f,xl,xu,es,imax,ea)
  iter=0;
  xr=0;
  while iter<=imax
     xrold=xr;
     xr=xl-f(xl)*(xu-xl)/(f(xu)-f(xl));
     iter=iter+1;
     if ne(xr,0)
       ea=abs((xr-xrold)/xr)*100;
     end
     xu=xl;
     xl=xr;
  end
    yy=xr;
end

fplot(f1,[0 1],'b')
grid on;
r1=secante(f1,0,1,1,4,2.6);
fprintf("El valor de la raiz es = %f \n",r1)