$v\in\mathbb{R}^3$, $\mid{v}\mid = \sqrt{v_1^2+v_2^2+v_3^2}$
The question, is the following a bilinear form, if yes than what matrix corresponds to it?$f(v,u)=\mid{v+u}\mid^2 - \mid{v}\mid^2 - \mid{u}\mid^2$
Edit: I got the help and got 2 downvotes, should I delete the question?
Expand the components of both vectors and you will find out.