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D( x )
x/3 = 0
x/3 = 0
x/3 = 0
1/3*x = 0 // : 1/3
x = 0
x in (-oo:0) U (0:+oo)
(X^3+3*x^2-(2*x)-6)/(x/3) = 0
(X^3+3*x^2-2*x-6)/(x/3) = 0
(X^3+3*x^2-2*x-6)/(1/3*x) = 0
X^3+3*x^2-2*x-6 = 0
DELTA = (-2)^2-(3*4*(X^3-6))
DELTA = 4-12*(X^3-6)
4-12*(X^3-6) = 0
4-12*(X^3-6) = 0
76-12*X^3 = 0
76-12*X^3 = 0
-12*X^3 = -76 // : -12
X^3 = 19/3
X^3 = 19/3 // ^ 1/3
X = (19/3)^(1/3)
DELTA = 0 <=> t_2 = (19/3)^(1/3)
x = 2/(2*3) i X = (19/3)^(1/3)
x = 1/3 i X = (19/3)^(1/3)
( x = ((4-12*(X^3-6))^(1/2)+2)/(2*3) or x = (2-(4-12*(X^3-6))^(1/2))/(2*3) ) i X > (19/3)^(1/3)
( x = ((4-12*(X^3-6))^(1/2)+2)/6 or x = (2-(4-12*(X^3-6))^(1/2))/6 ) i X > (19/3)^(1/3)
X-(19/3)^(1/3) > 0
X-(19/3)^(1/3) > 0 // + (19/3)^(1/3)
X > (19/3)^(1/3)
x in { 1/3, ((4-12*(X^3-6))^(1/2)+2)/6, (2-(4-12*(X^3-6))^(1/2))/6 }
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