function [xo,n]=falsi (f,a,b,tol,ftol)
    if (f(a)*f(b)<0)
        n=0;
        h = 10^(-5);
        pochodna=(f(a+h)-(2*f(a))+f(a-h))/h^2;
        if(f(a)*pochodna>0)
            xs=a;
            xo=b;
        else
            xs=b;
            xo=a;
        end
        while(1)
            n=n+1;
            xpop=xo;
            xo=xs-f(xs)*((xo-xs)/(f(xo)-f(xs)));
            if(abs(f(xo))<ftol)
                break;
            end
            if(abs(xpop-xo)<tol)
                break;
            end
        end
    end
end