Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Three-dimensional Geometry

Question:

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

Options:

0

1

$\sqrt{2}$

$2\sqrt{2}$

Correct Answer:

$2\sqrt{2}$

Explanation:

The equation of a plane passing through (1, -2, 1) is 

$a(x-1) + b(y+2)+c(z-1) = 0 $ .........(i)

It is perpendicular to 2x - 2y + z = 0 and x - y + 2z = 4.

$∴ 2a - 2b + c = 0 $ and $ a - b + 2c = 0 $

$ \frac{a}{-3}=\frac{b}{-3}=\frac{c}{0}$

Substituting the values of a, b, c in (i), we obtain

$ x + y + 1= 0 $

Distance of this plane from (1, 2, 2) is given by

$d = \frac{1+2+1}{\sqrt{1+1}}= 2\sqrt{2}$