JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Mock Test - Binomial Theorem

  • question_answer
    Let \[f(x)={{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...+{{a}_{n}}{{x}^{n}}+...\]and \[\frac{f(x)}{1-x}={{b}_{0}}+{{b}_{1}}x+{{b}_{2}}{{x}^{2}}+...+{{b}_{n}}{{x}^{n}}+....,\]then

    A) \[{{b}_{n}}={{b}_{n-1}}={{a}_{n}}\]

    B) \[{{b}_{n}}-{{b}_{n-1}}={{a}_{n}}\]

    C) \[{{b}_{n}}/{{b}_{n-1}}={{a}_{n}}\]

    D) none of these

    Correct Answer: B

    Solution :

    [b] \[\frac{f(x)}{1-x}={{b}_{0}}+{{b}_{1}}x+{{b}_{2}}{{x}^{2}}+...+{{b}_{n}}{{x}^{n}}+...\] \[\Rightarrow {{a}_{0}}+{{a}_{1}}x+{{a}_{2}}{{x}^{2}}+...+{{a}_{n}}{{x}^{n}}+...\] \[=(1-x)({{b}_{0}}+{{b}_{1}}x+{{b}_{2}}{{x}^{2}}+...+{{b}_{n}}{{x}^{n}}+...)\] Comparing the coefficient of \[{{x}^{n}}\]on both the sides, \[{{a}_{n}}={{b}_{n}}-{{b}_{n-1.}}\]


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