Question

The value of $\lambda$ for which $x+2y+7=0$ and $2x+\lambda y+14=0$ represent coincident lines is

• A. $3$
• B. $4$
• C. $-4$
• D. $-3$

Answer 1

Answer: (B)

$4$

The pair of lines represent coincident lines if
$\frac{a_1}{a_2}=\frac{b_1}{b_2}=\frac{c_1}{c_2}$
$\Rightarrow \frac{1}{2}=\frac{2}{\lambda }=\frac{7}{14}\Rightarrow \frac{2}{\lambda }=\frac{1}{2}$
$\Rightarrow \lambda =4$
Hence, the correct option is (B).