Q. In the interval (-3, 3) the function $f(x) = \frac{x}{3} + \frac{3}{x},\ x \neq 0$ is
A) increasing
B) Decreasing
C) Neither increasing nor decreasing
D) Party increasing and party decreasing
Explanation
(b)
Given, $f(x) = \frac{x}{3} + \frac{3}{x} \Rightarrow f^{''}(x) = \frac{1}{3} - \frac{3}{x^{2}}$
Put $f^{''}(x) = 0\ \Rightarrow x = \pm 3$
[image:6_image11.emf]
Thus, $f(x)$is decreasing in the interval $( - 3,3).$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.