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D( x )
3*x = 0
3*x = 0
3*x = 0
3*x = 0 // : 3
x = 0
x in (-oo:0) U (0:+oo)
2/(3*x) = 12-((2*x)/3) // - 12-((2*x)/3)
(2*x)/3+2/(3*x)-12 = 0
2/3*x^1+2/3*x^-1-12*x^0 = 0
(2/3*x^2-12*x^1+2/3*x^0)/(x^1) = 0 // * x^2
x^1*(2/3*x^2-12*x^1+2/3*x^0) = 0
x^1
(2/3)*x^2-12*x+2/3 = 0
(2/3)*x^2-12*x+2/3 = 0
DELTA = (-12)^2-(4*(2/3)*(2/3))
DELTA = 1280/9
DELTA > 0
x = ((1280/9)^(1/2)+12)/(2*(2/3)) or x = (12-(1280/9)^(1/2))/(2*(2/3))
x = 3/4*((1280/9)^(1/2)+12) or x = 3/4*(12-(1280/9)^(1/2))
x in { 3/4*(12-(1280/9)^(1/2)), 3/4*((1280/9)^(1/2)+12)}
x in { 3/4*(12-(1280/9)^(1/2)), 3/4*((1280/9)^(1/2)+12) }
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