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D( x )
3*x^3 = 0
3*x^3 = 0
3*x^3 = 0
3*x^3 = 0 // : 3
x^3 = 0
x = 0
x in (-oo:0) U (0:+oo)
(9*x^4-(27*x^6))/(3*x^3) = 0
(9*x^4-27*x^6)/(3*x^3) = 0
9*x^4-27*x^6 = 0
9*x^4*(1-3*x^2) = 0
-3*x^2 = -1 // : -3
x^2 = 1/3
x^2 = 1/3 // ^ 1/2
abs(x) = (1/3)^(1/2)
x = (1/3)^(1/2) or x = -(1/3)^(1/2)
9*x^4*(x-(1/3)^(1/2))*(x+(1/3)^(1/2)) = 0
(9*x^4*(x-(1/3)^(1/2))*(x+(1/3)^(1/2)))/(3*x^3) = 0
( 9*x^4 )
9*x^4 = 0 // : 9
x^4 = 0
x = 0
( x+(1/3)^(1/2) )
x+(1/3)^(1/2) = 0 // - (1/3)^(1/2)
x = -(1/3)^(1/2)
( x-(1/3)^(1/2) )
x-(1/3)^(1/2) = 0 // + (1/3)^(1/2)
x = (1/3)^(1/2)
x in { 0}
x in { -(1/3)^(1/2), (1/3)^(1/2) }
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