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NDA 2026
Exam
NDA
Year
2026
Subject
Mathematics
Chapter
Continuity and Differentiability

NDA 2026 · Mathematics · Continuity and Differentiability

Passage: Let f(x)= cases ax(x-1), & x 3 cases Given that f(x) is...

Passage: Let f(x)=f(x)=\begin{cases} ax(x-1), & x< 1 \\ x-1, & 1\leq x\leq3 \\ px^2+qx+2, & x > 3 \end{cases}$<br>Giventhat<br>Given thatf(x)iscontinuousforallis continuous for allxbutnotdifferentiableatbut not differentiable atx=1.Further. Furtherf'(x)iscontinuousatis continuous atx=3.<br><br><strong>Question:</strong>Whatisthevalueof.<br><br><strong>Question:</strong> What is the value ofq$ ?

Options

  1. A−1-1
  2. B−13-\dfrac{1}{3}
  3. C13\dfrac{1}{3}
  4. D11

Correct answer

A. −1-1

Step-by-step solution

For f(x)f(x) to be continuous at x=3x=3, we must have lim⁡x→3−f(x)=lim⁡x→3+f(x)\lim_{x \to 3^-} f(x) = \lim_{x \to 3^+} f(x).

3−1=p(3)2+q(3)+23 - 1 = p(3)^2 + q(3) + 2

2=9p+3q+22 = 9p + 3q + 2

9p+3q=0⇒3p+q=09p + 3q = 0 \Rightarrow 3p + q = 0

For f′(x)f'(x) to be continuous at x=3x=3, the left-hand derivative must equal the right-hand derivative at x=3x=3.

f′(x)=1f'(x) = 1 for 1<x<31 < x < 3

f′(x)=2px+qf'(x) = 2px + q for x>3x > 3

Equating the derivatives at x=3x=3:

1=2p(3)+q1 = 2p(3) + q

6p+q=16p + q = 1

Solving the two equations:

3p+q=03p + q = 0

6p+q=16p + q = 1

Subtracting the first equation from the second gives 3p=1⇒p=133p = 1 \Rightarrow p = \dfrac{1}{3}.

Substituting pp into the first equation gives q=−3(13)=−1q = -3\left(\dfrac{1}{3}\right) = -1.

Answer: −1-1
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