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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
4/x = (8/5)*x+4 // - (8/5)*x+4
4/x-((8/5)*x)-4 = 0
(-8/5)*x+4/x-4 = 0
4*x^-1-8/5*x^1-4*x^0 = 0
(4*x^0-8/5*x^2-4*x^1)/(x^1) = 0 // * x^2
x^1*(4*x^0-8/5*x^2-4*x^1) = 0
x^1
(-8/5)*x^2-4*x+4 = 0
(-8/5)*x^2-4*x+4 = 0
DELTA = (-4)^2-(4*4*(-8/5))
DELTA = 208/5
DELTA > 0
x = ((208/5)^(1/2)+4)/(2*(-8/5)) or x = (4-(208/5)^(1/2))/(2*(-8/5))
x = -5/16*((208/5)^(1/2)+4) or x = -5/16*(4-(208/5)^(1/2))
x in { -5/16*((208/5)^(1/2)+4), -5/16*(4-(208/5)^(1/2))}
x in { -5/16*((208/5)^(1/2)+4), -5/16*(4-(208/5)^(1/2)) }
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