If O be the origin and the coordinates of P be $(1,2, - 3)$, then, find the equation of the plane passing through P and perpendicular to O P.

The direction ratios of OP are $< 1 - 0,2 - 0, - 3 - 0 >$ i.e. $< 1,2, - 3 >$

$\therefore$ The equation of the plane passing through P and perpendicular to OP is
$(1)(x - 1) + (2)(y - 2) + ( - 3)(z + 3) = 0$

$\Rightarrow$ $x - 1 + 2y - 4 - 3z - 9 = 0 \Rightarrow x + 2y - 3z - 14 = 0$