To l4

clc;
clear all;

x1=10;
x2=20;

T=10^(-6);

eps=10^-8;

xk=[x1; x2];

rk=[ (f(x1+T,x2)-f(x1,x2))/T ;(f(x1,x2+T)-f(x1,x2))/T ];

pk=-rk;

%x1
%x2

while norm(rk)>eps

hk1= (f(x1+2*T,x2)-2*f(x1+T,x2)+f(x1,x2))/T^2;
hk2= (f(x1+T,x2+T)-f(x1+T,x2)-f(x1,x2+T)+f(x1,x2))/T^2;
hk3= (f(x1+T,x2+T)-f(x1+T,x2)-f(x1,x2+T)+f(x1,x2))/T^2;
hk4= (f(x1,x2+2*T)-2*f(x1,x2+T)+f(x1,x2))/T^2;

H=[hk1 hk2; hk3 hk4];
%theta=(rk'*rk)/(rk'*H*rk);
theta=-(pk'*rk)/(pk'*H*pk);

xk=xk+theta*pk;

x1=xk(1);
x2=xk(2);
rkv=rk;
rk=[ (f(x1+T,x2)-f(x1,x2))/T ;(f(x1,x2+T)-f(x1,x2))/T ];
beta=(rk'*rk)/(rkv'*rkv);
pk=-rk+beta*pk;

end;

%theta=(rk'*rk)/(rk'*(H*rk));
%q=xk+theta*hk
%q

xk