%As = sparse(A);
%M2 = (1-alpha)^2 * As' * A + (1-alpha) * (A' + A) * (alpha * S - Id) + (alpha^2 - 2*alpha) * S + Id;

N = sparse((1-alpha) * A - Id);
B = alpha * S;
M2 = N' * N + (N' + N + alpha * Id) * B;