Ok...

I have this question on a tutorial that i cant really figure out...

A fair die is thrown twice, and let X and Y be the resulting numbers. Let U = X - Y and V = X + Y. Show that Cov(U,V) = 0. Are U and V independant?

Now i know that if they are independant then this proves Cov(U,V) = 0 but i cant figure out if they are, and if they're not then ive no idea how to prove Cov(U,V) = 0.

Can anyone help on this?

Cheers