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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)
(6*x^7-(12*x^4))/(3*x^3) = 0
(6*x^7-12*x^4)/(3*x^3) = 0
6*x^7-12*x^4 = 0
6*x^4*(x^3-2) = 0
1*x^3 = 2 // : 1
x^3 = 2
x^3 = 2 // ^ 1/3
x = 2^(1/3)
6*x^4*(x-2^(1/3)) = 0
(6*x^4*(x-2^(1/3)))/(3*x^3) = 0
( 6*x^4 )
6*x^4 = 0 // : 6
x^4 = 0
x = 0
( x-2^(1/3) )
x-2^(1/3) = 0 // + 2^(1/3)
x = 2^(1/3)
x in { 0}
x = 2^(1/3)
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