371. Form the equation of the plane $Q$, which intercepts a segment $O A=3$ on the $O x$ axis and is perpendicular to the vector $\bar{n}\{2 ; -3 ; 1\}$.
Solution. According to the problem, point $A$ lies on the plane with coordinates $x=3, y=0, z=0$. Using formula (4), we obtain the equation of the desired plane

$$
2(x-3)-3 y+z=0
$$

or

$$
2 x-3 y+z=6
$$