JEE Main & Advanced Sample Paper JEE Main Sample Paper-14

  • question_answer
    The value of \[\underset{x\to \infty }{\mathop{\lim }}\,\,\,\left( \sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}}}}-\sqrt{3{{x}^{2}}} \right)\] is

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

    B)  \[-\frac{1}{2}\]

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

    D)  \[\sqrt{3}\]

    Correct Answer: A

    Solution :

     \[=\underset{x\to \infty }{\mathop{\lim }}\,\,\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}}}}-\sqrt{3{{x}^{2}}}\] \[=\underset{x\to \infty }{\mathop{\lim }}\,\,\frac{3{{x}^{2}}+\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}}}-3{{x}^{2}}}{\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}+\sqrt{3{{x}^{2}}}}}+\sqrt{3{{x}^{2}}}}\] (by rationalization) \[=\underset{x\to \infty }{\mathop{\lim }}\,\,\frac{\sqrt{3+\sqrt{\frac{3}{{{x}^{2}}}}}}{\sqrt{3+\sqrt{\frac{3}{{{x}^{2}}}}+\sqrt{\frac{3}{{{x}^{4}}}}+\sqrt{3}}}\] \[=\frac{\sqrt{3}}{\sqrt{3}+\sqrt{3}}=\frac{1}{2}\]


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