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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
2*x-(9/x)-4 = 0
2*x-9*x^-1-4 = 0
2*x^1-9*x^-1-4*x^0 = 0
(2*x^2-4*x^1-9*x^0)/(x^1) = 0 // * x^2
x^1*(2*x^2-4*x^1-9*x^0) = 0
x^1
2*x^2-4*x-9 = 0
2*x^2-4*x-9 = 0
DELTA = (-4)^2-(-9*2*4)
DELTA = 88
DELTA > 0
x = (88^(1/2)+4)/(2*2) or x = (4-88^(1/2))/(2*2)
x = (2*22^(1/2)+4)/4 or x = (4-2*22^(1/2))/4
x in { (4-2*22^(1/2))/4, (2*22^(1/2)+4)/4}
x in { (4-2*22^(1/2))/4, (2*22^(1/2)+4)/4 }
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