KVPY Sample Paper KVPY Stream-SX Model Paper-9

  • question_answer
    Let us define a region \[R\]in \[xy-\]plane as a set of points \[(x,y)\]satisfying \[\left[ {{x}^{2}} \right]\]=\[\left[ y \right]\](where \[\left[ x \right]\]denotes greatest integer \[\le x),\]then the region \[R\]defines

    A) a parabola whose axis is horizontal

    B) a parabola whose axis is vertical

    C) Integer point of the parabola \[y={{x}^{2}}\]

    D) none of the these

    Correct Answer: D

    Solution :

    \[\because \left[ {{x}^{2}} \right]=\left[ y \right]\]
    If \[0\le y<1,\]then,\[\left[ y \right]=0\]
    \[\therefore \left[ {{x}^{2}} \right]=0\Rightarrow 0\le {{x}^{2}}<1\Rightarrow x\in \left( -1,1 \right)\]
    For \[1\le y<2,then\left[ y \right]=1\therefore \left[ {{x}^{2}} \right]=1\]
    \[\Rightarrow 1\le {{x}^{2}}<2\Rightarrow x\in \left( -\sqrt{2,-1} \right)\cup \left( 1,\sqrt{2} \right)\]
    For \[2\le y<3,\]then\[\left[ y \right]=2\]then\[\left[ {{x}^{2}} \right]=2\]
    \[\Rightarrow 2\le {{x}^{2}}<3\]
    \[\therefore x\in \left( -\sqrt{3,}-\sqrt{2} \right)\cup \left( \sqrt{2,}\sqrt{3} \right)\]
    The graph of the region will not only contain of the parabola \[y={{x}^{2}}\]but \[\left[ {{x}^{2}} \right]\]=\[\left[ y \right]\]contain points within the rectangles of side 1, 2; \[1\sqrt{2}-1;1,\sqrt{3}-\sqrt{2}\]etc.
    Hence, [a] [b] and [c] are incorrect options.


You need to login to perform this action.
You will be redirected in 3 sec spinner