trootpar.asv

数值分析各种公式的解法

function trootpar(x0,x1,x2,eps)
k=0
while abs(x2-x1)>eps
    k=k+1
    p=x1;
    q=x2;
    v2=(x2-x1)/(x1-x0);
    w2=1+v2;
    a=f1(x0)*v2^2-f1(x1)*v2*w2+f1(x2)*v2;
    b=f1(x0)*v2^2-f1(x1)*w2^2+f1(x2)*(v2+w2);
    c=f1(x2)*w2;
    s=max(abs(b-sqrt(b^2-4*a*c)),abs(b+sqrt(b^2-4*a*c)));
    dd=abs(b-sqrt(b^2-4*a*c));
    if dd==s
        d=b+sqrt(b^2-4*a*c);
    else
        d=b-sqrt(b^2-4*a*c);
    end
    v3=-2*c/d
    x2=x2+v3*(x2-x1)
    x0=p;
    x1=q;
end
r=x2
function f1=f1(x)
f1=x*exp(x)-1