JEE Main & Advanced Mathematics Sequence & Series Question Bank Mock Test - Sequences and Series

  • question_answer
    If x, 2y, 3z are in A.P. where the distinct numbers x, y, z are in G.P., then the common ratio of the G.P. is

    A) 3                     

    B) \[\frac{1}{3}\]

    C) 2                    

    D) \[\frac{1}{2}\]

    Correct Answer: B

    Solution :

    [b] x, y, and z are in G.P. Hene, \[y=xr,\,\,z=x{{r}^{2}}\] Also, x, 2y, and 3z are in A.P. Hence, \[4y=x+3z\] \[\Rightarrow 4xr=x+3x{{r}^{2}}\] \[\Rightarrow 3{{r}^{2}}-4r+1=0\] \[\Rightarrow (3r-1)(r-1)=0\] \[\Rightarrow r=1/3\](\[r\ne 1\]is not possible as x, y, z are distinct)


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