We denote the initial guess for \( \hat{x} \) as \( \hat{x}_0 \). We can assume without loss of generality that
$$ \begin{equation*} \hat{x}_0=0, \end{equation*} $$or consider the system
$$ \begin{equation*} \hat{A}\hat{z} = \hat{b}-\hat{A}\hat{x}_0, \end{equation*} $$instead.