Question:

A plane passes through $ (1 ,-2 ,1 )$ and is perpendicular to two planes $2x - 2y + z = 0$ and $x - y + 2z = 4, $ then the distance of the plane from the point $ (1, 2, 2)$ is

Updated On: Jun 14, 2022
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  • $\sqrt 2$
  • $2 \sqrt 2$
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The Correct Option is D

Solution and Explanation

Let the equation of plane be
$\, \, \, \, \, a\, (x-1) +b\, (y+2)+c\, (z-1) = 0$
which is perpendicular to $ 2 x- 2y + z = 0$ and
$ x - y + 2z = 4.$
$\Rightarrow$ $\hspace10mm 2a- 2b +c = 0\, \, and\, \, a - b + 2c = 0 $
$\Rightarrow$ $\hspace15mm \frac{a}{-3} = \frac{b}{-3} = \frac{c}{0} $
$\Rightarrow$ $\hspace20mm \frac{a}{1} = \frac{b}{1} = \frac{c}{0}.$
So, the equation of plane i s $ x - l + y + 2 = 0 $
or $\hspace70mm x + y + 1 = 0 $
Its distance from the point (1, 2, 2) is
$\hspace50mm \frac{|\, 1\, +\, 2\, +\, 1\, |}{ \sqrt2}= 2 \sqrt 2$
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