Q. If $( - 4,\ 5)$ is one vertex and $7x - y + 8 = 0$ is one diagonal of a square, then the equation of the second diagonal is
A) $x + 3y = 21$
B) $2x - 3y = 7$
C) $x + 7y = 31$
D) $2x + 3y = 21$
Explanation
(c)
Equation of perpendicular diagonal to $7x - y + 8 = 0$ is $x + 7y = \lambda$, which passes through $( - 4,\ 5)$
$\therefore\ \lambda = 31$
So, equation of another diagonal is
$x + 7y = 31$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.