Question

If the co-ordinates of the points P and Q be (1, –2, 1) and

(2, 3, 4) and O be the origin, then

• A. $O P = O Q$
• B. $O P \perp O Q$
• C. $O P \| O Q$
• D. None of these

Answer 1

Answer: (B)

$O P \perp O Q$

Answer 2

$a _ { 1 } a _ { 2 } + b _ { 1 } b _ { 2 } + c _ { 1 } c _ { 2 } = 0$ so $O P \perp O Q$ .