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JEE Main & Advanced Sample Paper JEE Main Sample Paper-17

  • question_answer
    An infinite G.R has 2nd term as\[x\] and its sum is  4. Then \[x\] belongs to                      

    A) \[(0,2]\]                              

    B) \[(1,8)\]

    C) \[(-8,1]\]                             

    D)  None of these

    Correct Answer: C

    Solution :

     \[\text{Sum}=\frac{\frac{x}{r}}{1-r}=4\](where \[r\]is common ratio) \[x=4r(1-r)\]                 \[=4(r-{{r}^{2}})\] For         \[r\in (-1,1),\]                 \[r-{{r}^{2}}\in \left( -2,\frac{1}{4} \right)\] \[\Rightarrow \]               \[x\in (-8,1]\]


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