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

  • question_answer
    \[\frac{1}{1.2}+\frac{1.3}{1.2.3.4}+\frac{1.3.5}{1.2.3.4.5.6}+....\infty =\]

    A) \[\sqrt{e}\]        

    B) \[\sqrt{e}+1\]

    C) \[\sqrt{e}-1\]

    D) \[e-1\]

    Correct Answer: C

    Solution :

    [c] \[{{T}_{n}}=\frac{1.3.5.......(2n-1)}{(2n)!}\] \[=\frac{1.2.3.4....(2n-1).2n}{(2n)!2.\,4.\,6.....2n}\] \[=\frac{(2n)!}{(2n)!{{2}^{n}}n!}=\frac{1}{{{2}^{n}}n!}\] Now putting \[n=1,2,3,.........\] we see that the sum of series \[S=\frac{1}{2}+\frac{{{(1/2)}^{2}}}{2!}+\frac{{{(1/2)}^{3}}}{3!}+....\] \[={{e}^{\frac{1}{2}}}-1=\sqrt{e}-1\]


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