Q. If $\alpha$ is a repeated root of $ax^{2} + bx + c = 0$, then $\lim_{x \rightarrow \alpha}\frac{\sin{(ax^{2} + bx + c)}}{(x - \alpha)^{2}}$ is

A) 0
B) $a$
C) $b$
D) $c$
Explanation

(b)
Since, $\alpha$ is a repeated root.
$\therefore\ \ \ \ \ ax^{2} + bx + c = a(x - \alpha)^{2}$
Now, $\lim_{x \rightarrow \alpha}\frac{\sin{(ax^{2} + bx + c)}}{(x - \alpha)^{2}}$
$= \lim_{x \rightarrow \alpha}\frac{\sin{a(x - \alpha)^{2}}}{a(x - \alpha)^{2}} \times a$
$= \lim_{x \rightarrow \alpha}{a(1) =}a$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.