Question 1102632
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The necessary and sufficient condition for it is <U>THIS</U>:


    The polynomial (the function)  x^4 - 4x^2 + k  is always positive (and never zero or negative).


In turn, the necessary and sufficient condition for it is <U>THIS</U>:

   
    The polynomial  y^2 -4y + k  is always positive.


In turn, the necessary and sufficient condition for it is <U>THIS</U>:


    The discriminant  d = 4^2 - 4k is negative:


    16 - 4k < 0  ====>  16 < 4k  ====>  4 < k.


<U>Answer</U>.  k > 4.
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