Question

If the line through the points $A(4, 1, 2), B (5, \lambda, 0)$ is p arallel to the line joining the points $C(2, 1, 1)$ and $D(3, 3, -1)$ then the value of $\lambda$ equals

• A. $1$
• B. $3$
• C. $2$
• D. $-3$

Answer 1

Answer: (B)

dr’s of $AB$ are $<\, 1, \lambda -1 , -2 \,>$
dr’s of C D are $<\, 1, 2, -2 \, >$
As $AB || CD$
$\therefore 1 = \frac{\lambda-1}{2} = \frac{-2}{-2}$
$\Rightarrow \lambda=3$