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

  • question_answer
    \[\frac{(2n)!}{{{2}^{2n}}{{(n!)}^{2}}}\,\,is\,\,\le \]

    A) \[\frac{1}{3n+1}\]       

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

    C) \[\frac{1}{{{(3n+1)}^{2}}}\]  

    D) \[\frac{1}{{{(3n+1)}^{1/2}}}\]

    Correct Answer: B

    Solution :

    [b] By setting\[n=1,\]we get \[\frac{2n!}{{{2}^{2n}}.{{(n!)}^{2}}}\]as \[\frac{2}{{{2}^{2}}.{{(1)}^{2}}}=\frac{2}{4}=\frac{1}{2}.\]
    Second alternative gives \[\frac{1}{2}\].
    Upon setting \[n=2,\frac{2n!}{{{2}^{2n}}.{{(n)}^{2}}}\]becomes \[\frac{3}{8}\], second alternative
    Becomes \[\frac{1}{\sqrt{7}}\]which is greater than \[\frac{3}{8}.\]


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