Question

The d.r's of two parallel lines are $4,-3,-1$ and $\lambda +\mu ,1+\mu ,2$ then $(\lambda ,\mu )$ is:

• A. $(1,7)$
• B. $(-1,-7)$
• C. $(7,1)$
• D. $(-13,5)$

Answer 1

The correct option is D $(-13,5)$

For lines to be parallel, $\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}\Rightarrow \frac{4}{\lambda +\mu }=\frac{-3}{1+\mu }=\frac{-1}{2}$
On solving, we have: $\lambda =-13,\mu =5$