Medium MCQ +4 / -1 PYQ · JEE Mains 2020

For all twice differentiable functions f : R $\to$ R,
with f(0) = f(1) = f'(0) = 0

  1. A f''(x) $\ne$ 0, at every point x $\in$ (0, 1)
  2. B f''(x) = 0, for some x $\in$ (0, 1) Correct answer
  3. C f''(0) = 0
  4. D f''(x) = 0, at every point x $\in$ (0, 1)

Solution

f : R $\to$ R, with f(0) = f(1) = 0 <br>and f'(0) = 0 <br>$\because$ f(x) is differentiable and continuous <br>and f(0) = f(1) = 0 <br><br>Applying Rolle’s theorem in [0, 1] for function f(x) <br>f'(c) = 0, c $\in$ (0, 1) <br><br>Now again <br>$\because$ f'(c) = 0, f'(0) = 0 <br>again applying Rolles theorem in [0, c] for function f'(x) <br>f''(c<sub>1</sub>) = 0 for some c<sub>1</sub> $\in$ (0, c) $\in$ (0, 1)

About this question

Subject: Mathematics · Chapter: Limits, Continuity and Differentiability · Topic: Limits and Standard Results

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