Question:

If the distance of the point $P (1, - 2,1)$ from the plane $x + 2y - 2z = a$, where $a > 0$, is $5$, then the foot of the perpendicular form $ P$ to the plane is

Updated On: Jun 14, 2022
  • $\bigg(\frac{8}{3},\frac{4}{3},-\frac{7}{3}\bigg)$
  • $\bigg(\frac{4}{3},\frac{4}{3},\frac{1}{3}\bigg)$
  • $\bigg(\frac{1}{3},\frac{2}{3},\frac{10}{3}\bigg)$
  • $\bigg(\frac{2}{3},\frac{1}{3},\frac{5}{2}\bigg)$
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The Correct Option is A

Solution and Explanation

Distance of point P from plane = 5
$\therefore \hspace15mm 5= \bigg|\frac{1-4-2-\alpha}{3}\bigg| $
$\Rightarrow \hspace15mm \alpha =0 $
Foot of perpendicular
$\hspace30mm \frac{x-1}{1} = \frac{y+2}{2} = \frac{z-1}{-2}= \frac{5}{3}$
$\Rightarrow \hspace30mm x=\frac{8}{3}, y = \frac{4}{3},z = - \frac{7}{3}$
Thus, the foot of the perpendicular is $ A \bigg(\frac{8}{3}, \frac{4}{3},- \frac{7}{3}\bigg).$
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