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

  • question_answer
    The sum of the coefficients of even power of x in the expansion of \[{{(1+x+{{x}^{2}}+{{x}^{3}})}^{5}}\]is [EAMCET 1988]

    A) 256

    B) 128

    C) 512

    D) 64

    Correct Answer: C

    Solution :

    \[{{(1+x+{{x}^{2}}+{{x}^{3}})}^{5}}={{(1+x)}^{5}}{{(1+{{x}^{2}})}^{5}}\]\[=(1+5x+10{{x}^{2}}+10{{x}^{3}}+5{{x}^{4}}+{{x}^{5}})\]\[\times (1+5{{x}^{2}}+10{{x}^{4}}+10{{x}^{6}}+5{{x}^{8}}+{{x}^{10}})\] Therefore the required sum of coefficients\[=(1+10+5){{.2}^{5}}=16\times 32=512\] Note: \[{{2}^{n}}={{2}^{5}}\]= Sum of all the binomial coefficients in the 2nd bracket in which all the powers of x are even.


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