JEE Main & Advanced Mathematics Conic Sections Question Bank Self Evaluation Test - Conic Sections

  • question_answer
    The number of points (a, b) where a and b are positive integers lying on the hyperbola \[{{x}^{2}}-{{y}^{2}}=512\] is

    A) 3

    B) 4

    C) 5

    D) 6

    Correct Answer: B

    Solution :

    [b] \[{{a}^{2}}-{{b}^{2}}=512\Rightarrow (a+b)(a-b)={{2}^{9}}\] \[\Rightarrow (a+b,a-b)=({{2}^{8}},2),({{2}^{7}},{{2}^{2}}),({{2}^{6}},{{2}^{3}}),({{2}^{5}},{{2}^{4}})\] Since \[a>b,a+b>a-b\] therefore the other combinations like \[({{2}^{4}},{{2}^{5}})\] etc. cannot be accepted \[({{2}^{9}},1)\] also cannot be accepted since a and b are positive integers. 


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