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

Let [t] denote the greatest integer $\le$ t. If for some
$\lambda$ $\in$ R - {1, 0}, $$\mathop {\lim }\limits_{x \to 0} \left| {{{1 - x + \left| x \right|} \over {\lambda - x + \left[ x \right]}}} \right|$$ = L, then L is equal to :

  1. A 1
  2. B 2 Correct answer
  3. C 0
  4. D ${1 \over 2}$

Solution

Here $$\mathop {\lim }\limits_{x \to 0} \left| {{{1 - x + \left| x \right|} \over {\lambda - x + [x]}}} \right| = L$$<br><br>Here L.H.L. $$\mathop {\lim }\limits_{h \to 0^-} \left| {{{1 + h + h} \over {\lambda + h - 1}}} \right| = \left| {{1 \over {\lambda - 1}}} \right|$$<br><br>R.H.L. = $$\mathop {\lim }\limits_{h \to 0^+} \left| {{{1 - h + h} \over {\lambda + h + 0}}} \right| = \left| {{1 \over \lambda }} \right|$$<br><br>$\because$ Limit exists. Hence L.H.L. = R.H.L.<br><br>$\Rightarrow$ $\left| {\lambda - 1} \right| = \left| \lambda \right|$<br><br>$\Rightarrow$ $\lambda = {1 \over 2}$ <br><br>$\therefore$ L = ${1 \over {\left| \lambda \right|}}$ = 2

About this question

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

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