310. Find the distance between the points $A(3; -4; -1)$ and $B(-1; 2; -3)$.
Solution. Using formula (15), we get

$$
d=|\overline{A B}|=\sqrt{(-1-3)^{2}+(2+4)^{2}+(-3+1)^{2}}=\sqrt{56} \approx 7.48
$$