Q. The condition for a line $y = 2x + c$ to touch the circle $x^{2} + y^{2} = 16$ is
A) $c = 10$
B) $c^{2} = 80$
C) $c = 12$
D) $c^{2}\text{=}64$
Explanation
(b)
Here, $c = c,\ m = 2,\ a^{2} = 16$
$\because\ \ \ c^{2} = a^{2}\left( 1 + m^{2} \right)\ \ \therefore\ \ \ c^{2} = 16(1 + 4)$
$\Rightarrow \ \ \ c^{2} = 80$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.