If $(2,-1,3)$ is the foot of the perpendicular drawn from the origin to the plane, then the equation of the plane is

Where $a, b, c$ are the direction ratios. Since, point $O(0,0,0$,$) is perpendicular to the foot of$ the plane at a point $P(2,-1,3)$. $\therefore \quad$ Direction's of $O P=2,-1,3$ Since the line $O P$ is perpendicular to the plane, therefore the direction's of the normal to the plane is proportional to the direction is of $O P$ $\therefore$ Required equation of plane is $$ \begin{array}{rlrl} & 2(x-2)-1(y+1)+3(z-3) & =0 \\ \Rightarrow & 2 x-y+3 z-14 =0 \end{array} $$