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

  • question_answer
    \[\underset{n\to \infty }{\mathop{\lim }}\,\frac{{{2}^{-n}}({{n}^{2}}+5n+6)}{(n+4)\,(n+5)}\] is equal to

    A)  \[0\]

    B)  \[1\]

    C)  \[\infty \]

    D)  \[-\infty \]

    Correct Answer: A

    Solution :

    \[\underset{x\to \infty }{\mathop{\lim }}\,\frac{{{2}^{-n}}({{n}^{2}}+5n+6)}{(n+4)(n+5)}\] \[=\underset{x\to \infty }{\mathop{\lim }}\,\frac{{{n}^{2}}\left( 1+\frac{5}{n}+\frac{6}{{{n}^{2}}} \right)}{{{2}^{n}}.{{n}^{2}}\left( 1+\frac{4}{n} \right)\left( 1+\frac{5}{n} \right)}\] \[=\underset{x\to \infty }{\mathop{\lim }}\,\frac{{{n}^{2}}\left( 1+\frac{5}{n}+\frac{6}{{{n}^{2}}} \right)}{{{2}^{n}}\left( 1+\frac{4}{n} \right)\left( 1+\frac{5}{n} \right)}=0\]


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