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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
9/x = x+9/4 // - x+9/4
9/x-x-(9/4) = 0
9/x-x-9/4 = 0
9*x^-1-1*x^1-9/4*x^0 = 0
(9*x^0-1*x^2-9/4*x^1)/(x^1) = 0 // * x^2
x^1*(9*x^0-1*x^2-9/4*x^1) = 0
x^1
(-9/4)*x-x^2+9 = 0
(-9/4)*x-x^2+9 = 0
DELTA = (-9/4)^2-(-1*4*9)
DELTA = 657/16
DELTA > 0
x = ((657/16)^(1/2)-(-9/4))/(-1*2) or x = (-(-9/4)-(657/16)^(1/2))/(-1*2)
x = ((657/16)^(1/2)+9/4)/(-2) or x = (9/4-(657/16)^(1/2))/(-2)
x in { ((657/16)^(1/2)+9/4)/(-2), (9/4-(657/16)^(1/2))/(-2)}
x in { ((657/16)^(1/2)+9/4)/(-2), (9/4-(657/16)^(1/2))/(-2) }
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