JEE Main & Advanced Mathematics Sequence & Series Question Bank Relation between AP., GP. and HP.

  • question_answer
    If \[a,\ b,\ c\] are in H.P., then for all \[n\in N\] the true statement is [RPET 1995]

    A) \[{{a}^{n}}+{{c}^{n}}<2{{b}^{n}}\]

    B) \[{{a}^{n}}+{{c}^{n}}>2{{b}^{n}}\]

    C) \[{{a}^{n}}+{{c}^{n}}=2{{b}^{n}}\]

    D) None of the above

    Correct Answer: B

    Solution :

    For two numbers \[a\] and \[c\] \[\frac{{{a}^{n}}+{{c}^{n}}}{2}>{{\left( \frac{a+c}{2} \right)}^{n}}\]    (Where\[n\in N,\ n>1\]) \[\because \]\[A.M.>G.M.>H.M.\] \[\therefore \]\[\frac{a+b}{2}>b\]           \[(\because \ a,\ b,\ c\] are in H.P.) \[\Rightarrow \]\[{{\left( \frac{a+c}{2} \right)}^{n}}>{{b}^{n}}\]\[\Rightarrow \]\[\frac{{{a}^{n}}+{{c}^{n}}}{2}>{{\left( \frac{a+c}{2} \right)}^{n}}>{{b}^{n}}\].


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