JEE Main & Advanced Sample Paper JEE Main Sample Paper-46

  • question_answer
    The number of positive integral solutions of \[{{x}^{4}}-{{y}^{4}}=3789108\] is

    A)  0                                

    B)  1                 

    C)  2                                

    D)  4

    Correct Answer: A

    Solution :

     Since, RHS is an even integer. Then LHS is an even integer. So, either both \[x\] and \[y\] are even integers or both of there are odd integers. Now, \[{{x}^{4}}-{{y}^{4}}=\,(x-y)(x+y)\,({{x}^{2}}+{{y}^{2}})\] \[\Rightarrow \] \[x-y,\,x+y,\,{{x}^{2}}+{{y}^{2}}\] must be an even integer. Therefore, \[(x-y)\,(x+y)\,({{x}^{2}}+{{y}^{2}})\] must be divisible by 8 and but RHS is not divisible by 8. Hence, the given equation has no solution.


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