function xjf(x,y,e,f)
x1=x;
y1=y;
syms t
f1=inline(f);
f2=diff(f1(t));
f5=inline(f2);
xx=linspace(x,y,100);
for i=2:100;
    yy(i)=(f1(xx(i))-f1(xx(1)))/(xx(i)-xx(1));
end
yy(1)=0;
if yy~=ones(1,100);
    syms t2
    f3=inline(t2-f1(t2)/f5(t2));
    syms t1
    y1=diff(f3(t1));
    f2=inline(y1);
    xx1=linspace(x,y,100);
    s=abs(f2(xx));
    s1=zeros(1,100);
    s2=ones(1,100);
    if s>s1 & s<s2;
        i=0;
        while abs(x-y)>e;
            w=x;
            x=y;
            y=x-f1(x)*(x-x1)/(f1(x)-f1(x1));
            i=i+1;
            fprintf('%d%13.8f\n',i,y);
        end
    else 
        disp('此多項式不能進行迭代');
    end
else
    disp('此多項式不能進行迭代');
end