Q. The value of $f(0)$, so that the function $f(x) = \frac{\sqrt{a^{2} - ax + x^{2}} - \sqrt{a^{2} + ax + x^{2}}}{\sqrt{a + x} - \sqrt{a - x}}$ Becomes continuous for all $x$, is given by

A) $a^{3/2}$
B) $a^{1/2}$
C) $- a^{1/2}$
D) $- a^{3/2}$
Explanation

(c)
$f(x) = \frac{\sqrt{a^{2} - ax + x^{2}} - \sqrt{a^{2} + ax + x^{2}}}{\sqrt{a + x} - \sqrt{a - x}} \times \frac{\sqrt{a^{2} - ax + x^{2}} + \sqrt{a^{2} + ax + x^{2}}}{\sqrt{a^{2} - ax + x^{2}} + \sqrt{a^{2} + ax + x^{2}}} \times \frac{\sqrt{a + x} + \sqrt{a - x}}{\sqrt{a + x} + \sqrt{a - x}}$
$\Rightarrow \lim_{x \rightarrow 0}\ f(x)$
$= \lim_{x \rightarrow 0}\ \frac{- 2ax(\sqrt{a + x} + \sqrt{a - x})}{2x\ (\sqrt{a^{2} - ax + x^{2}} + \sqrt{a^{2} + ax + x^{2})}}$
$= \frac{- a(2\sqrt{a})}{(a + a)} = - \sqrt{a}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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