BCECE Engineering BCECE Engineering Solved Paper-2005

  • question_answer
    \[\int_{0}^{1}{x{{(1-x)}^{4}}dx}\]is equal to:

    A)  1                            

    B)         0                            

    C)  \[\frac{1}{30}\]                   

    D)         \[\frac{1}{5}\]

    Correct Answer: C

    Solution :

    Let          \[I=\int_{0}^{1}{x{{(1-x)}^{4}}dx}\] \[=\int_{0}^{1}{(1-x){{(1-(1-x))}^{4}}dx}\] \[=\int_{0}^{1}{(1-x){{x}^{4}}dx}\] \[=\int_{0}^{1}{({{x}^{4}}-{{x}^{5}})dx}\] \[=\left[ \frac{{{x}^{5}}}{5}-\frac{{{x}^{6}}}{6} \right]_{0}^{1}=\left[ \frac{1}{5}-\frac{1}{6} \right]\] \[=\frac{1}{30}\] Alternate Solution: Let          \[I=\int_{0}^{1}{x{{(1-x)}^{4}}dx}\]                 \[=\left[ -x\frac{{{(1-5)}^{5}}}{5} \right]_{0}^{1}-\int_{0}^{1}{-\frac{{{(1-x)}^{5}}}{5}}dx\]                 \[=0+\frac{1}{5}\left[ -\frac{{{(1-x)}^{6}}}{6} \right]_{0}^{1}\]                 \[=-\frac{1}{5}\left( 0-\frac{1}{6} \right)=\frac{1}{30}\]


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