J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    \[\underset{x\to -1}{\mathop{\lim }}\,\frac{1+\sqrt[3]{x}}{1+\sqrt[5]{x}}\]is equal to

    A)  \[\frac{5}{3}\]             

    B)  \[\frac{3}{7}\]

    C)  \[\frac{4}{7}\]           

    D)  \[\frac{-3}{5}\]

    Correct Answer: A

    Solution :

    \[\underset{x\to -1}{\mathop{\lim }}\,\frac{1+{{x}^{\frac{1}{2}}}}{1+{{x}^{\frac{1}{5}}}}=\underset{x\to -1}{\mathop{\lim }}\,\frac{a+\frac{1}{3}{{x}^{-\frac{2}{3}}}}{0+\frac{1}{5}{{x}^{-\frac{4}{5}}}}\] (using L? Hospital?s rule) \[=\underset{x\to -1}{\mathop{\lim }}\,\frac{5}{3}{{x}^{\frac{4}{5}-\frac{2}{3}}}\] \[=\underset{x\to -1}{\mathop{\lim }}\,\frac{5}{3}{{(x)}^{\frac{2}{15}}}=\frac{5}{3}{{[{{(-1)}^{2}}]}^{\frac{1}{15}}}=\frac{5}{3}\]


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