J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{{{e}^{5x}}-{{e}^{4x}}}{x}\]is equal to

    A)  \[1\]

    B)  \[2\]

    C)  \[4\]

    D)  \[5\]

    Correct Answer: A

    Solution :

    \[\underset{x\to 0}{\mathop{\lim }}\,\,\frac{{{e}^{5x}}-{{e}^{4x}}}{x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\left[ \begin{align}   & \left( 1+\frac{5x}{1!}+\frac{{{(5x)}^{2}}}{2!}+.... \right)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\  & -\left( 1+\frac{4x}{11}+\frac{{{(4x)}^{2}}}{2!}+..... \right) \\ \end{align} \right]}{x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\,\,\,\,\frac{x\left[ \left( \frac{5}{1!}+\frac{25x}{2!}+..... \right)-\left( \frac{4}{1!}+\frac{16x}{2!}+.... \right) \right]}{x}\] \[=1\]


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