Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Continuity and Differentiability

Question:

Let $f(x)=\left\{\begin{array}{l}\frac{x}{2 x^2+|x|}, & x \neq 0 \\ 1, & x=0\end{array}\right.$, then f(x) is

Options:

Continuous but non−differentiable at x = 0

Is differentiable at x = 0

Discontinuous at x = 0

none of these

Correct Answer:

Discontinuous at x = 0

Explanation:

$f(0+0)=\lim\limits_{h \rightarrow 0} f(-h)$

$=\lim\limits_{h \rightarrow 0} \frac{h}{2 h^2+h}$

$=\lim\limits_{h \rightarrow 0} \frac{1}{2 h+1}=1$

and $f(0 - 0)=\lim\limits_{h \rightarrow 0} f(-h)$

$=\lim\limits_{h \rightarrow 0} \frac{-h}{2 h^2+|-h|}$

$=\lim\limits_{h \rightarrow 0} \frac{-h}{2 h^2+h}$

$=\lim\limits_{h \rightarrow 0} \frac{-1}{2 h+1}=-1$

as f(0 + 0) ≠ f(0 – 0), thus f(x) is discontinuous at x = 0.