JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to a}{\mathop{\lim }}\,\frac{({{x}^{-1}}-{{a}^{-1}})}{x-a}=\] [MP PET 1994]

    A)                 \[{{x}_{n+1}}=\sqrt{2+{{x}_{n}}},\ n\ge 1,\ \]

    B)                 \[\frac{-1}{a}\]

    C)                 \[\frac{1}{{{a}^{2}}}\]

    D)                 \[\frac{-1}{{{a}^{2}}}\]

    Correct Answer: D

    Solution :

                    \[\underset{x\to a}{\mathop{\lim }}\,\,\frac{(1/x)-(1/a)}{x-a}=\underset{x\to a}{\mathop{\lim }}\,\,\frac{a-x}{ax\,(x-a)}=\underset{x\to a}{\mathop{\lim }}\,\,\frac{-1}{ax}=\frac{-1}{{{a}^{2}}}\].


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