I need to create an iterative code to find the minimum of the function

f(x)=1/2*Transpose(x)*A*x-Transpose(x)*b

where x and b are vectors in R^2 and A is a 2X2 symmetric positive definite matrix. The implications of this is that the gradient of the function is

gradf=A*x-b

and that we are indeed searching for a minimum.

This is the code I have so far, using the while command to create a loop.