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D( x )
x^2 = 0
x^2 = 0
x^2 = 0
1*x^2 = 0 // : 1
x^2 = 0
x = 0
x in (-oo:0) U (0:+oo)
(x/2)*x-(81/(x^2))+18+81 = 0
(x/2)*x-81*x^-2+18+81 = 0
1/2*x^2-81*x^-2+99 = 0
t_1 = x^2
1/2*t_1^1-81*t_1^-1+99 = 0
1/2*t_1^1-81*t_1^-1+99*t_1^0 = 0
(1/2*t_1^2+99*t_1^1-81*t_1^0)/(t_1^1) = 0 // * t_1^2
t_1^1*(1/2*t_1^2+99*t_1^1-81*t_1^0) = 0
t_1^1
(1/2)*t_1^2+99*t_1-81 = 0
(1/2)*t_1^2+99*t_1-81 = 0
DELTA = 99^2-(-81*4*(1/2))
DELTA = 9963
DELTA > 0
t_1 = (9963^(1/2)-99)/(2*(1/2)) or t_1 = (-9963^(1/2)-99)/(2*(1/2))
t_1 = 9*123^(1/2)-99 or t_1 = -9*123^(1/2)-99
t_1 in { -9*123^(1/2)-99, 9*123^(1/2)-99}
t_1 = -9*123^(1/2)-99
x^2-(-9*123^(1/2))+99 = 0
x^2+9*123^(1/2)+99 = 0
1*x^2 = -(9*123^(1/2)+99) // : 1
x^2 = -(9*123^(1/2)+99)
t_1 = 9*123^(1/2)-99
x^2-(9*123^(1/2))+99 = 0
x^2-9*123^(1/2)+99 = 0
1*x^2 = -(99-9*123^(1/2)) // : 1
x^2 = -(99-9*123^(1/2))
x^2 = -(99-9*123^(1/2)) // ^ 1/2
abs(x) = (-(99-9*123^(1/2)))^(1/2)
x = (-(99-9*123^(1/2)))^(1/2) or x = -(-(99-9*123^(1/2)))^(1/2)
x in { (-(99-9*123^(1/2)))^(1/2), -(-(99-9*123^(1/2)))^(1/2) }
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