Question

The point in which the join of A(- 9, 4, 5) and B(11, 0, -1) is met by the perpendicular from the origin

• A. (2, 2, 1)
• B. (2, 1, 2)
• C. (1, 2, 2)
• D. (2, 2, 2)

Answer 1

The correct option is C

(1, 2, 2)

Let P be the required point on AB. Let P divides AB in the ratio $\lambda$:1

P = ($\frac{11\lambda -9}{\lambda +1}$,$\frac{4}{\lambda +1}$,$\frac{5-\lambda }{\lambda +1}$) , OP⊥ AB ⇒ 20($\frac{11\lambda -9}{\lambda +1}$)-4($\frac{4}{\lambda +1}$)-6($\frac{5-\lambda }{\lambda +1}$)=0

$\therefore$ $\lambda$=1 ⇒ P=(1,2,2)