JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,(\sqrt{{{x}^{2}}+8x+3}-\sqrt{{{x}^{2}}+4x+3})=\]        [MP PET 1997]

    A)                 0

    B)                 \[\infty \]

    C)                 2

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

    Correct Answer: C

    Solution :

     On rationalization \[\underset{x\to \infty }{\mathop{\lim }}\,\,\frac{4x}{(\sqrt{{{x}^{2}}+8x+3}+\sqrt{{{x}^{2}}+4x+3}}\]                                                 \[=\underset{x\to \infty }{\mathop{\lim }}\,\,\frac{4}{\left( \sqrt{1+\frac{8}{x}+\frac{3}{{{x}^{2}}}}+\sqrt{1+\frac{4}{x}+\frac{3}{{{x}^{2}}}} \right)}=2\].


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