JEE Main & Advanced Mathematics Sequence & Series Question Bank nth term of special series, Sum to n terms and Infinite number of terms

  • question_answer
    The sum to \[n\] terms of the series \[{{2}^{2}}+{{4}^{2}}+{{6}^{2}}+...........\] is  [MP PET 1994]

    A) \[\frac{n(n+1)(2n+1)}{3}\]

    B) \[\frac{2n(n+1)(2n+1)}{3}\]

    C) \[\frac{n(n+1)(2n+1)}{6}\]

    D) \[\frac{n(n+1)(2n+1)}{9}\]

    Correct Answer: B

    Solution :

    \[{{2}^{2}}+{{4}^{2}}+{{6}^{2}}+........+{{(2n)}^{2}}\]                               \[={{2}^{2}}({{1}^{2}}+{{2}^{2}}+{{3}^{2}}+.......+{{n}^{2}})\] \[=\frac{4n(n+1)(2n+1)}{6}=\frac{2n(n+1)(2n+1)}{3}\].


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