Question

if the straight lines $2x+5ay-1=0$ and $3x+7y+7=0$ are mutually perpendicular, then value of $a$ is

• A. $\frac{6}{37}$
• B. $\frac{-6}{31}$
• C. $\frac{-6}{37}$
• D. $\frac{-6}{35}$

Answer 1

Answer: (D)

$\frac{-6}{35}$

Answer 2

Given, straight lines $2x+5ay-1=0$
and $3x+7y+7=0$ are mutually perpendicular.
Therefore, ${{m}_{1}}{{m}_{2}}=-1$
$\frac{-2}{5a}\times \frac{-3}{7}=-1$
$\Rightarrow$ $a=\frac{-6}{35}$