JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Properties of binomial coefficients

  • question_answer
    In the expansion of \[{{(1+x)}^{50}},\] the sum of the coefficient of odd powers of x is                [UPSEAT 2001; Pb. CET 2004]

    A) 0

    B) \[{{2}^{49}}\]

    C) \[{{2}^{50}}\]

    D) \[{{2}^{51}}\]

    Correct Answer: B

    Solution :

    We have, \[{{(1+x)}^{50}}=\sum\limits_{r=0}^{50}{{}^{50}{{C}_{r}}{{x}^{r}}}\]. Therefore, sum of coefficients of odd power of x = \[{}^{50}{{C}_{1}}+{}^{50}{{C}_{3}}+...+{}^{50}{{C}_{49}}\]   = \[\frac{1}{2}[{}^{50}{{C}_{0}}+{}^{50}{{C}_{1}}+...+{}^{50}{{C}_{50}}]\,\,=\,\,\frac{1}{2}[{{2}^{50}}]={{2}^{49}}\].


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