\[ \mathcal{K}_m = \mathrm{span}( b, A^{} b, A^2 b,\ldots, A^{m-1} b ),\]
where the approximate solution $x_m$ resides.
In practice, an orthonormal basis $V_m$ that spans the
subspace $\mathcal{K}_{m}$ can be generated by
\[ \mathcal{K}_m = \mathrm{span}( b, A^{} b, A^2 b,\ldots, A^{m-1} b ),\]
where the approximate solution $x_m$ resides.
In practice, an orthonormal basis $V_m$ that spans the
subspace $\mathcal{K}_{m}$ can be generated by