CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2000

  • question_answer
    \[\int{{{a}^{x}}{{e}^{x}}}dx\]is equal to:

    A)  \[{{a}^{x}}{{e}^{x}}+c\]               

    B)         \[\left[ \frac{{{a}^{x}}{{e}^{x}}}{\log a} \right]+c\]          

    C)         \[\left[ \frac{{{(ae)}^{x}}}{(x+1)} \right]+c\]      

    D)         \[\left[ \frac{{{a}^{x}}{{e}^{x}}}{1+\log a} \right]+c\]

    E)  \[\frac{{{e}^{x}}{{a}^{x}}}{(a+1)}+c\]

    Correct Answer: D

    Solution :

    Let \[I=\int{{{(ae)}^{x}}}dx=\int{{{a}^{x}}{{e}^{x}}}dx\] \[\Rightarrow \]               \[I=\int{{{a}^{x}}{{e}^{x}}}dx\]                  \[=\frac{{{a}^{x}}}{\log a}{{e}^{x}}-\int{{{e}^{x}}\frac{{{a}^{x}}}{\log a}}dx\] \[\Rightarrow \]               \[I=\frac{{{a}^{x}}{{e}^{x}}}{\log a}-\frac{I}{\log a}\] \[\Rightarrow \]               \[I+\frac{I}{\log a}=\frac{{{a}^{x}}{{e}^{x}}}{\log a}\] \[\Rightarrow \]               \[(\log a+1)I={{a}^{x}}{{e}^{x}}\] \[\Rightarrow \]               \[I=\frac{{{a}^{x}}{{e}^{x}}}{\log a+1}+c\]


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