%斯蒂芬森迭代法求解 
%令x=(x^2+exp(x)+2)/3

x=1.5;
y=fun(x);
z=fun(y);
x1=x-(y-x)^2/(z-2*y+x);
while(abs(x1-x)>1e-6)
    x=x1;
    y=fun(x);
    z=fun(y);
    x1=x-(y-x)^2/(z-2*y+x);
end
b=x1;
fprintf('%.6f\n',b)