function  erci
syms x;
f=8*x^3-2*x^2-7*x+3; % 目标函数
al=0; a2=1;
a3=2; % 插值区间
k=0;
while (abs(a3-al)>0.01) % 精度
fl=subs(f,x,al);
f2=subs (f,x,a2);
f3=subs(f,x,a3);
Cl=(f3-fl)/(a3-al);
C2=((f2-fl)/(a2-al)-Cl)/(a2-a3);
ap=0.5*(al+a3-Cl/C2);
fp=subs(f,x,ap);
if ap>a2;
if f2>=fp;
al=a2;
f1=f2;
a2=ap;
f2=fp;
else
a3=ap;
f3=fp;
end
else
if f2>=fp;
    a3=a2;
    f3=f2;
a2=ap;
f2=fp;
else
al=ap;
fl=fp;
end
end
k=k+l;
  a=ap;
   ff=subs(f,x,ap);
end