Calulate norms of orthogonals vectors

Question

I need to calculate $(||2u+3v||^2 - ||2u-3v||^2)$ knowing that u and v are orthogonal.
I don't understand how i can calculate without any information on those vectors and why the fact that these vectors are orthogonal help to that.

Answer 1

Hint

For any vectors $x,y$, you have

$$\Vert x \Vert^2 - \Vert y\Vert^2 =\langle x-y , x+y \rangle$$