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

The value of $$\mathop {\lim }\limits_{n \to \infty } {1 \over n}\sum\limits_{j = 1}^n {{{(2j - 1) + 8n} \over {(2j - 1) + 4n}}} $$ is equal to :

  1. A $5 + {\log _e}\left( {{3 \over 2}} \right)$
  2. B $2 - {\log _e}\left( {{2 \over 3}} \right)$
  3. C $3 + 2{\log _e}\left( {{2 \over 3}} \right)$
  4. D $1 + 2{\log _e}\left( {{3 \over 2}} \right)$ Correct answer

Solution

$$\mathop {\lim }\limits_{n \to \infty } {1 \over n}\sum\limits_{j = 1}^n {{{\left( {{{2j} \over n} - {1 \over n} + 8} \right)} \over {\left( {{{2j} \over n} - {1 \over n} + 4} \right)}}} $$<br><br>$$\int\limits_0^1 {{{2x + 8} \over {2x + 4}}dx = \int\limits_0^1 {dx + \int\limits_0^1 {{4 \over {2x + 4}}} dx} } $$<br><br>$= 1 + 4{1 \over 2}(\ln |2x + 4|)_0^1$<br><br>$= 1 + 2\ln \left( {{3 \over 2}} \right)$

About this question

Subject: Mathematics · Chapter: Definite Integration · Topic: Fundamental Theorem of Calculus

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