J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,{{\left( \frac{{{x}^{2}}+5x+3}{{{x}^{2}}+x+2} \right)}^{x}}\] is equal to

    A)  \[e\]

    B)  \[{{e}^{2}}\]

    C)  \[{{e}^{3}}\]

    D)  \[{{e}^{4}}\]

    Correct Answer: D

    Solution :

    \[\underset{x\to \infty }{\mathop{\lim }}\,{{\left( \frac{{{x}^{2}}+5x+3}{{{x}^{2}}+x+2} \right)}^{x}}\] \[=\underset{x\to \infty }{\mathop{\lim }}\,{{\left( 1+\frac{4x+1}{{{x}^{2}}+x+2} \right)}^{x\times \frac{{{x}^{2}}+x+2}{4x+1}\times \frac{4x+1}{{{x}^{2}}+x+2}}}\] \[={{e}^{\underset{x\to \infty }{\mathop{\lim }}\,\frac{4{{x}^{2}}+x}{{{x}^{2}}+x+2}}}\] \[={{e}^{\underset{x\to \infty }{\mathop{\lim }}\,\frac{4+\frac{1}{x}}{1+\frac{1}{x}+\frac{2}{{{x}^{2}}}}}}={{e}^{4}}\]


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