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How To Solve X^2-4x-7=0?

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Oddman answered
You can solve this by "completing the square." I find it easier to put the constant by itself on one side of the equal sign for that.
  x^2 - 4x - 7 = 0
  x^2 - 4x = 7          (add 7 to both sides)
  x^2 - 4x + 4 = 7 + 4  (complete the square by adding (4/2)^2)
  (x - 2)^2 = 11      (simplify)
  x - 2 = ±√11        (square root both sides)
  x = 2 ± √11        (add 2 to both sides)

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