JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    The value of \[\underset{x\to 7}{\mathop{\lim }}\,\frac{2-\sqrt{x-3}}{{{x}^{2}}-49}\] is [MP PET 2003]

    A)                 \[\frac{2}{9}\]

    B)                 \[-\frac{2}{49}\]

    C)                 \[\frac{1}{56}\]

    D)                 \[-\frac{1}{56}\]

    Correct Answer: D

    Solution :

                       Applying L-Hospital?s rule,            \[\underset{x\to 7}{\mathop{\lim }}\,\frac{2-\sqrt{x-3}}{{{x}^{2}}-49}\] = \[\underset{x\to 7}{\mathop{\lim }}\,\frac{0-\frac{1}{2\sqrt{x-3}}}{2x}\]                                              \[=\underset{x\to 7}{\mathop{\lim }}\,\frac{-1}{4x\sqrt{x-3}}=\frac{-1}{4.7\sqrt{7-3}}=\frac{-1}{56}\].


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