Medium MCQ +4 / -1 PYQ · JEE Mains 2021

Let f(x) be a differentiable function defined on [0, 2] such that f'(x) = f'(2 $-$ x) for all x$\in$ (0, 2), f(0) = 1 and f(2) = e2. Then the value of $\int\limits_0^2 {f(x)} dx$ is :

  1. A 1 + e<sup>2</sup> Correct answer
  2. B 2(1 + e<sup>2</sup>)
  3. C 1 $-$ e<sup>2</sup>
  4. D 2(1 $-$ e<sup>2</sup>)

Solution

f'(x) = f'(2 $-$ x)<br><br>On integrating both side f(x) = $-$f(2 $-$ x) + c<br><br>put x = 0<br><br>f(0) + f(2) = c $\Rightarrow$ c = 1 + e<sup>2</sup><br><br>$\Rightarrow$ f(x) + f(2 $-$ x) = 1 + e<sup>2</sup> ..... (i)<br><br>$$I = \int\limits_0^2 {f(x)dx} = \int\limits_0^1 {\{ f(x) + f(2 - x)\} dx = (1 + {e^2})} $$

About this question

Subject: Mathematics · Chapter: Definite Integration · Topic: Properties of Definite Integrals

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