How can I use while or for in first gradient method?

syms x1;

syms x2;

f = 2*x1^2 + 3*x2^2 - 5*x1*x2 + 10*x1 + 5*x2

gr1=diff(f, x1);

x0=[2;2];

gr1=subs(gr1, x1, x0(1));

gr1=subs(gr1, x2, x0(2));

gr2=diff(f, x2);

gr2=subs(gr2, x1, x0(1));

gr2=subs(gr2, x2, x0(2));

gr=[gr1; gr2]

D=(gr)/(sqrt(gr1^2 + gr2^2));

D=[8*113^(1/2)/113; 7*113^(1/2)/113]

S=1;

x01=x0-S*D

fx01= 2*x01(1)^2 + 3*x01(2)^2 - 5*x01(1)*x01(2) + 10*x01(1) + 5*x01(2)

prm=sqrt(D(1)^1 + D(2)^2)

fx0=2*x0(1)^2 + 3*x0(2)^2 - 5*x0(1)*x0(2) + 10*x0(1) + 5*x0(2);

doa=fx0-fx01

epsilon=0.1;

[Jan]

The question is not clear, because you did not mention the purpose of the loop. Then it is impossible to guess reliably, where it has to be inserted with which conditions. Please edit the question an add the details.