JEE Main & Advanced JEE Main Solved Paper-2014

  • question_answer
    If \[a\in R\]and the equation \[-3{{(x-[x])}^{2}}+2(x-[x])+{{a}^{2}}=0\](where [x] denotes the greatest integer ≤ x) has no integral solution, then all possible values of alie in the interval:   JEE Main  Solved  Paper-2014

    A) \[(-1,0)\cup (0,1)\]         

    B) \[(-2,-1)\]                           

    C) \[(-\infty ,-2)\cup (2,\infty )\]

    Correct Answer: A

    Solution :

    \[-3{{\left( x-[x] \right)}^{2}}+2\left( x-[x] \right)+{{a}^{2}}=0\] \[-3{{\{x\}}^{2}}+2\{x\}+{{a}^{2}}=0\]                                    ?.(1) \[\therefore \]\[\{x\}=\frac{-2\pm \sqrt{4+12{{a}^{2}}}}{-6}=\frac{1\overline{+}\sqrt{1+3{{a}^{2}}}}{3}\] As\[0\le \{x\}<1\]                            \[0\le \frac{1+\sqrt{1+3{{a}^{2}}}}{3}<1\] \[-1\le \sqrt{1+3{{a}^{2}}}<2\] \[1+3{{a}^{2}}<4\] \[3({{a}^{2}}-1)<0\]                         \[a\in (-1,1)\] but it a = 0then equation (1)has integral solution So, \[a\ne 0\]                 \[a\in (-1,0)\cup (0,1)\] (b)\[(1,2)\]


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