Could anyone explain me this formula?
https://wikimedia.org/api/rest_v1/media/math/render/svg/14d5feb68844edae9e31c9cb4a2197ee922e409c
$$\langle \mathbf v_1 - \mathbf v_2, \mathbf x_1 - \mathbf x_2 \rangle =\ ?$$ $$\left\|\mathbf x_1 - \mathbf x_2\right\|^2 =\ ?$$
I guess $\langle a,b\rangle$, where $a,b\in\mathbb{R}^n$, refers to the scalar product.
Regarding $\|a\|^2$, I suppose it is the corresponding norm: $\|a\|^2=\langle a,a\rangle$.