falsi rule

function xc = mfp(f, a, b, k)
    if f(a)*f(b)>0
        error('error');
    end
    for i=1:k
        c = (b*f(a) - a*f(b))/(f(a)-f(b));
        if f(c)==0
            break
        end
        if f(a) * f(c) < 0
            b = c;
        else
            a = c;
        end
    end
    xc = c;
end