JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{n\to \infty }{\mathop{\lim }}\,{{({{3}^{n}}+{{4}^{n}})}^{\frac{1}{n}}}=\] [Karnataka CET 2003]

    A)                 3

    B)                 4

    C)                 \[\infty \]

    D)                 e

    Correct Answer: B

    Solution :

                       \[\underset{n\to \infty }{\mathop{\text{lim}}}\,\,{{({{3}^{n}}+{{4}^{n}})}^{\frac{1}{n}}}\] \[=\underset{n\to \infty }{\mathop{\text{lim}}}\,\,{{({{4}^{n}})}^{\frac{1}{n}}}{{\left[ \frac{{{3}^{n}}}{{{4}^{n}}}+1 \right]}^{\frac{1}{n}}}\]                    \[=\underset{n\to \infty }{\mathop{\text{lim}}}\,4\,{{\left[ 1+\frac{1}{{{\left( \frac{4}{3} \right)}^{n}}} \right]}^{1/n}}\]\[=4\underset{n\to \infty }{\mathop{\text{lim}}}\,\,{{\left[ 1+\frac{1}{{{\left( \frac{4}{3} \right)}^{n}}} \right]}^{1/n}}\]                                 \[=4{{\left[ 1+\frac{1}{\infty } \right]}^{0}}=4\times {{(1)}^{0}}\] \[=4\times 1=4\].


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