JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Multinomial theorem, Terms free from radical sign in the expansion(a1/p+b1/q), Problems regarding to three four consecutive terms or coefficients

  • question_answer
    The coefficient of two consecutive terms in the expansion of \[{{(1+x)}^{n}}\] will be equal, if

    A)  n is any integer

    B) n is an odd integer

    C)  n is an even integer

    D) None of these

    Correct Answer: B

    Solution :

    Let consecutive terms are \[^{n}{{C}_{r}}\]and \[^{n}{{C}_{r+1}}\] \[\Rightarrow \frac{n!}{(n-r)!r!}=\frac{n!}{(n-r-1)!(r+1)!}\] \[\Rightarrow \frac{1}{(n-r)(n-r-1)!r!}=\frac{1}{(n-r-1)!(r+1)r!}\] \[\Rightarrow r+1=n-r\,\Rightarrow n=2r+1\]. Hence n is odd.


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