Manipal Engineering Manipal Engineering Solved Paper-2010

  • question_answer
    The number of terms in the expansion of\[{{(\sqrt{5}+\sqrt[4]{11})}^{124}}\]which are integers, is equal to

    A)  0                                            

    B)  30    

    C)  31                         

    D)         32

    Correct Answer: D

    Solution :

    The general term in the expansion of\[{{(\sqrt{5}+4\sqrt{11})}^{124}}\]is                 \[{{T}_{r+1}}{{=}^{124}}{{C}_{r}}{{(\sqrt{5})}^{124-r}}{{(\sqrt[4]{11})}^{r}}\]                 \[{{=}^{124}}{{C}_{r}}\cdot {{5}^{(124-r)/2}}\cdot {{11}^{r/4}}\] For integer terms\[r=0,\,\,4,\,\,8,\,\,12,...,124\] \[\therefore \]Number of terms which are integers\[=32\]


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