Can you solve this linear algebra problem?

Prove that if u and v are vectors in R^n...
then ...
llu+vll^2 + llu-vll^2 = 2 llull^2 + 2 llvll^2
Update: This isn't homework, I'm not stupid... I know the answer, I'm posting the question to see if anyone else did... and obviously no one does...
4 answers 4