Question

If the product of distances of the point (1, 1, 1) from the origin and the plane $x - y + z + k = 0$ be 5, then k =

• A. – 2
• B. –3
• C. 4
• D. 7

Answer 1

Answer: (C)

4

Answer 2

$\sqrt { 1 + 1 + 1 } \cdot \left( \frac { 1 - 1 + 1 + k } { \sqrt { 3 } } \right) = \pm 5$ or $k = \pm 5 - 1 = 4 , - 6$.