JCECE Engineering JCECE Engineering Solved Paper-2006

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

    A) \[{{e}^{4}}\]                                      

    B) \[{{e}^{2}}\]

    C) \[{{e}^{3}}\]                                      

    D) \[e\]

    Correct Answer: A

    Solution :

    \[\underset{x\to \infty }{\mathop{\lim }}\,\left[ 1+\frac{4x+1}{{{x}^{2}}+x+2} \right]\]                 \[=\underset{x\to \infty }{\mathop{\lim }}\,{{(1+\alpha )}^{1/\alpha }}{{]}^{\alpha \,\,x}}\] where   \[\alpha =\frac{4x+1}{{{x}^{2}}+x+2}\] \[=\frac{4+\frac{1}{x}}{x\left( 1+\frac{1}{x}+\frac{2}{{{x}^{2}}} \right)}\to 4\]as\[x\to \infty \] Given limit\[={{e}^{4}}\]


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