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

  • question_answer
    Three non-zero real numbers form an A.P. and the squares of these numbers taken in the same order form a G.P. Then the number of all possible common ratios of the G.P. is

    A) 1

    B) 2

    C) 3

    D) None of these

    Correct Answer: C

    Solution :

    Let the numbers be\[a-d,\ a,\ a+d\]. Then \[{{(a-d)}^{2}},\ {{a}^{2}},\ {{(a+d)}^{2}}\] are in G.P. \[\therefore \]\[{{a}^{4}}={{(a-d)}^{2}}{{(a+d)}^{2}}\]\[\Rightarrow \]\[{{d}^{4}}-2{{a}^{2}}{{d}^{2}}=0\] \[\Rightarrow \]\[d=0,\ \pm \sqrt{2}a\] Hence \[d\] has three values.


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