Manipal Engineering Manipal Engineering Solved Paper-2009

  • question_answer
    \[\frac{1}{{{e}^{3x}}}({{e}^{x}}+{{e}^{5x}})={{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...\]\[\Rightarrow \,\,\,2{{a}_{1}}+{{2}^{3}}{{a}_{3}}+{{2}^{5}}{{a}_{5}}+...\]is equal to

    A) \[e\]                                     

    B) \[{{e}^{-1}}\]

    C)  1                            

    D)         0

    Correct Answer: D

    Solution :

    Given,\[\frac{1}{{{e}^{3x}}}({{e}^{x}}+{{e}^{5x}})={{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...\] \[\Rightarrow \]               \[({{e}^{-2x}}+{{e}^{2x}})={{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...\] \[\Rightarrow \]               \[2\left[ 1+\frac{{{(2x)}^{2}}}{2!}+\frac{{{(2x)}^{4}}}{4!}+... \right]\]                 \[={{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...\] \[\Rightarrow \]               \[{{a}_{1}}={{a}_{3}}={{a}_{5}}=...=0\] \[\therefore \]  \[2{{a}_{1}}+{{2}^{3}}{{a}_{3}}+{{2}^{5}}{{a}_{5}}+...=0\]


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