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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Continuity and Differentiability

NDA 2025 · Mathematics · Continuity and Differentiability

Consider the following for the two (02) items that follow: Let f(x)...

Consider the following for the two (02) items that follow:
Let f(x)=f(x) =\begin{cases} x^3, & x^2 < 1 \\ x^2, & x^2 \geq 1 \end{cases}$.<br><br>Considerthefollowingstatements:<br>I.Thefunctioniscontinuousat.<br><br>Consider the following statements:<br>I. The function is continuous atx = -1.<br>II.Thefunctionisdifferentiableat.<br>II. The function is differentiable atx = 1$.
Which of the statements given above is/are correct?

Options

  1. AI only
  2. BII only
  3. CBoth I and II
  4. DNeither I nor II

Correct answer

D. Neither I nor II

Step-by-step solution

The given function can be rewritten as:

f(x)=f(x) =\begin{cases} x^2, & x \leq -1 \\ x^3, & -1 < x < 1 \\ x^2, & x \geq 1 \end{cases}$<br><br>Checkingcontinuityat<br><br>Checking continuity atx = -1:<br>LeftHandLimit(LHL):<br>Left Hand Limit (LHL)= \lim_{x \to -1^-} x^2 = (-1)^2 = 1<br>RightHandLimit(RHL)<br>Right Hand Limit (RHL)= \lim_{x \to -1^+} x^3 = (-1)^3 = -1<br>SinceLHL≠RHL,<br>Since LHL ≠ RHL,f(x)isnotcontinuousatis not continuous atx = -1.StatementIisincorrect.<br><br>Checkingdifferentiabilityat. Statement I is incorrect.<br><br>Checking differentiability atx = 1:<br>First,checkcontinuityat:<br>First, check continuity atx = 1:<br>LHL:<br>LHL= \lim_{x \to 1^-} x^3 = 1<br>RHL<br>RHL= \lim_{x \to 1^+} x^2 = 1<br><br>f(1) = 1^2 = 1<br>Thefunctioniscontinuousat<br>The function is continuous atx = 1.<br><br>Now,checkthederivativesat.<br><br>Now, check the derivatives atx = 1:<br>LeftHandDerivative(LHD):<br>Left Hand Derivative (LHD)= \lim_{x \to 1^-} \dfrac{d}{dx}(x^3) = \lim_{x \to 1^-} 3x^2 = 3(1)^2 = 3<br>RightHandDerivative(RHD)<br>Right Hand Derivative (RHD)= \lim_{x \to 1^+} \dfrac{d}{dx}(x^2) = \lim_{x \to 1^+} 2x = 2(1) = 2<br>SinceLHD≠RHD,<br>Since LHD ≠ RHD,f(x)isnotdifferentiableatis not differentiable atx = 1$. Statement II is incorrect.

Both statements are incorrect.

Answer: Neither I nor II
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