CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2010

  • question_answer
    \[\int{(x+1){{(x+2)}^{7}}}(x+3)dx\]is equal to

    A)  \[\frac{{{(x+2)}^{10}}}{10}-\frac{{{(x+2)}^{8}}}{8}+C\]

    B)  \[\frac{{{(x+1)}^{2}}}{2}-\frac{{{(x+2)}^{8}}}{8}-\frac{{{(x+3)}^{2}}}{2}+C\]

    C)  \[\frac{{{(x+2)}^{10}}}{10}+C\]

    D)  \[\frac{{{(x+1)}^{2}}}{2}+\frac{{{(x+2)}^{8}}}{8}+\frac{{{(x+3)}^{2}}}{2}+C\]

    E)  \[\frac{{{(x+2)}^{9}}}{9}-\frac{{{(x+2)}^{7}}}{7}+C\]

    Correct Answer: A

    Solution :

    Let\[I=\int{(x+1){{(x+2)}^{7}}(x+3)}dx\] Putting \[x+2=t\] \[\Rightarrow \]               \[dx=dt\] Also,\[x+1=t-1\]and \[x+3=t+1\] \[\therefore \]  \[I=\int{(t-1){{t}^{7}}}(t+1)dt\]                 \[=\int{({{t}^{2}}-1)}{{t}^{7}}dt\]                 \[=\int{{{t}^{9}}}dt-\int{{{t}^{7}}}dt\]                 \[=\frac{{{t}^{10}}}{10}-\frac{{{t}^{8}}}{8}+c\]                 \[=\frac{{{(x+2)}^{10}}}{10}-\frac{{{(x+2)}^{8}}}{8}+c\]


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