JEE Main & Advanced JEE Main Paper (Held On 8 April 2017)

  • question_answer
    \[\underset{x\to 3}{\mathop{\lim }}\,\frac{\sqrt{3x}-3}{\sqrt{2x}-4-\sqrt{2}}\]is equal to: [JEE Online 08-04-2017]

    A) \[\frac{1}{\sqrt{2}}\]                                     

    B) \[\frac{1}{2\sqrt{2}}\]

    C) \[\frac{\sqrt{3}}{2}\]                                     

    D) \[\sqrt{3}\]

    Correct Answer: A

    Solution :

                    \[\underset{x\to 3}{\mathop{\lim }}\,\frac{\sqrt{3x}-3}{\sqrt{2x-4}-\sqrt{2}}\]                 Rationalize                 \[\underset{x\to 3}{\mathop{\lim }}\,\frac{(3x-9)\times \left( \sqrt{2x-4}+\sqrt{2} \right)}{\{\left( 2x-4 \right)-2\}\times \left( \sqrt{3x}+3 \right)}\] \[=\underset{x\to 3}{\mathop{\lim }}\,\frac{\left( 3x-3 \right)}{2\left( x-3 \right)}\times \frac{\sqrt{2x-4}+\sqrt{2}}{\left( \sqrt{3}x+3 \right)}\] \[=\frac{3}{2}\times \frac{2\sqrt{2}}{6}=\frac{1}{\sqrt{2}}\]        


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