Quadratic equation   (in our case  ) has the following solutons: 
   
    
   
  For these solutions to exist, the discriminant   should not be a negative number. 
   
  First, we need to compute the discriminant  :  . 
   
  Discriminant d=0 is zero! That means that there is only one solution:  . 
      Expression can be factored:   
   
    Again, the answer is: 0.571428571428571, 0.571428571428571.
Here's your graph: 
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