Geometric sum of a zeta zero equals analytic contination part Re^2 and Im^2

(*start*)
Clear[x, k, j];
k = 10000;
x = N[ZetaZero[1], 40];
k*(Re[Sum[1/x^n, {n, 1, k}]]^2 + Im[Sum[1/x^n, {n, 1, k}]]^2)
Re[k^(1 - x)/(x - 1)]^2 + Im[k^(1 - x)/(x - 1)]^2
%% - %
(*end*)

49.9898883372313974154830224669178291603

49.98988833723139741548302246691782916

0.*10^-36