Let K be a positive definite nxn matrix with eigenvalues 1 > 2 >

Let K be a positive definite nxn matrix with eigenvalues λ1 > λ2 > ∙ ∙ ∙ > λn > 0. For what values of e does the iterative system u(k+1) = u(k) + εr(k), where r(k) = f - K u(k) is the current residual vector, converge to the solution? What is the optimal value of ε and what is the convergence rate?