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D( z )
z = 0
z = 0
z = 0
z in (-oo:0) U (0:+oo)
(1/2)*z+1/z = 1/2 // - 1/2
(1/2)*z+1/z-(1/2) = 0
(1/2)*z+1/z-1/2 = 0
1/2*z^1+1*z^-1-1/2*z^0 = 0
(1/2*z^2-1/2*z^1+1*z^0)/(z^1) = 0 // * z^2
z^1*(1/2*z^2-1/2*z^1+1*z^0) = 0
z^1
(1/2)*z^2+(-1/2)*z+1 = 0
(1/2)*z^2+(-1/2)*z+1 = 0
DELTA = (-1/2)^2-(1*4*(1/2))
DELTA = -7/4
DELTA < 0
z in { }
z belongs to the empty set
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