БДЗ3 / newton

clc,clear

%fun = x.^2 + x*y + 2*y.^2 - a*x - b*y + c;
%diff_x = 2*x + y - a;
%diff_y = x + 4*y - b;
%diff2x = 2, diff2y = 4, diffxy = 1, diffyx = 1


a = 6.1;
b = 11.8;
c = 9.24;
e = 0.1;

x_y = [3;4];

H = [2 1; 1 4];


while true

grad_x = 2*x_y(1) + x_y(2) - a;
grad_y = x_y(1) + 4*x_y(2) - b;


if (abs(grad_x)<e && abs(grad_y)<e)
break
end

grad = [grad_x;grad_y];

x_y = x_y - inv(H)*grad;


end

x = x_y(1);
y = x_y(2);

fun_value = x.^2 + x*y + 2*y.^2 - a*x - b*y + c
x
y