Suppose I have a pair of solutions of the one dimensional massless complex wave equation in 1+1 dimensional spacetime, solutions with equal and opposite momentum in some rest frame, Ψ+ = exp[-i(Et+px)] Ψ- = exp[-i(Et-px)] Does it matter if 1) I sum Ψ+ and Ψ- and then preform a Lorentz Transformation, or 2) preform the Lorentz Transformation, L.T., on Ψ+ and Ψ- and then sum? L. T. [f(x,t)+g(x,t)] = [L.T. f(x,t)]+[L.T. g(x,t)] ? I think the answer is it should not matter the order of operation but I am having trouble simplifying my algebra. Just wondering if there is light at the end of the tunnel. Thanks for any help!