Question 1150729
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The discriminant  d = b^2 - 4ac must be zero:


    (-4k)^2 - 4*4k = 0


    16k^2 = 16k


      k = 1


      k = 0   ---  degenerated case.     


      If  k = 1, then  the equation is   x^2 + 4x + 4 = 0,  {{{(x+2)^2}}} = 0  ====>  The solution is   x= -2.
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Solved.