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JEE Main & Advanced Sample Paper JEE Main Sample Paper-15

  • question_answer
    The constant  term in the expansion of \[{{\left( x+\frac{1}{{{x}^{4}}} \right)}^{12}}\]is

    A)  260                                       

    B)  220

    C)  105                                       

    D)  none of these

    Correct Answer: D

    Solution :

    \[{{T}_{r+1}}{{=}^{n}}{{C}_{r}}{{x}^{n-r}}{{y}^{r}}\] \[{{=}^{12}}{{C}_{r}}{{x}^{12-r}}{{y}^{-4r}}\] \[{{=}^{12}}{{C}_{r}}{{x}^{12-5}}^{r}\] Now,\[12-5r=0\Rightarrow r=\frac{12}{5}\] Which is not possible.


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