Prove that if a vector u, is perpendicular to both v and w, then u is also perpendicular to v+w. More generally, show that u (perp) (sv+tw) for all scalars s and t.
I was thinking that the cross product would be relevant.
The Attempt at a Solution
I'm not quite sure where to start. I tried to use w[-wy, wx] and so forth, but I honestly don't understand their full meanings. Any help would be appreciated