%f=@(x)x.^3-2*x-1;
 %f=@(x)x.^3-2*x.^2+4*x-3;
 %f=@(x)x.^3-2*x-1;
 f=@(x)x.^2-4;
 x1 = 1;
 x2 = 3;
 tol=0.01;
x=dejen_secant_2019(f,x1,x2,tol);