Question

If O is the origin and $O P = 3$with direction ratios $- 1,2 , - 2$ , then co-ordinates of P are

• A. (1, 2, 2)
• B. $( - 1,2 , - 2 )$
• C. (–3, 6, –9)
• D. $( - 1 / 3,2 / 3 , - 2 / 3 )$

Answer 1

Answer: (B)

$( - 1,2 , - 2 )$

Answer 2

Co-ordinates of P are $( l r , m r , n r )$

Here $l = \frac { - 1 } { \sqrt { 1 ^ { 2 } + 2 ^ { 2 } + 2 ^ { 2 } } } = \frac { - 1 } { 3 } , m = \frac { 2 } { 3 } , n = \frac { - 2 } { 3 }$

and $r = 3$ ,(given)

∴ Co-ordinates of P are (–1, 2, –2).