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D( x )
-2*u^2*x^3 = 0
-2*u^2*x^3 = 0
-2*u^2*x^3 = 0
-2*u^2*x^3 = 0 // : -2*u^2
x^3 = 0
x = 0
x in (-oo:0) U (0:+oo)
(11*u^4*x-(6*u^4*x^7))/(-2*u^2*x^3) = 0
(11*u^4*x-6*u^4*x^7)/(-2*u^2*x^3) = 0
11*u^4*x-6*u^4*x^7 = 0
u^4*x*(11-6*x^6) = 0
-6*x^6 = -11 // : -6
x^6 = 11/6
x^6 = 11/6 // ^ 1/6
abs(x) = (11/6)^(1/6)
x = (11/6)^(1/6) or x = -(11/6)^(1/6)
u^4*x*(x-(11/6)^(1/6))*(x+(11/6)^(1/6)) = 0
(u^4*x*(x-(11/6)^(1/6))*(x+(11/6)^(1/6)))/(-2*u^2*x^3) = 0
( u^4*x )
u^4*x = 0 // : u^4
x = 0
( x+(11/6)^(1/6) )
x+(11/6)^(1/6) = 0 // - (11/6)^(1/6)
x = -(11/6)^(1/6)
( x-(11/6)^(1/6) )
x-(11/6)^(1/6) = 0 // + (11/6)^(1/6)
x = (11/6)^(1/6)
x in { 0}
x in { -(11/6)^(1/6), (11/6)^(1/6) }
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