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D( z )
6/z+8 = 0
z = 0
6/z+8 = 0
6/z+8 = 0
6*z^-1 = -8 // : 6
z^-1 = -4/3
-1 < 0
1/(z^1) = -4/3 // * z^1
1 = -4/3*z^1 // : -4/3
-3/4 = z^1
z = -3/4
z = 0
z = 0
z in (-oo:-3/4) U (-3/4:0) U (0:+oo)
(10/z+8)/(6/z+8) = 0
(10*z^-1+8)/(6*z^-1+8) = 0
10*z^-1 = -8 // : 10
z^-1 = -4/5
-1 < 0
1/(z^1) = -4/5 // * z^1
1 = -4/5*z^1 // : -4/5
-5/4 = z^1
z = -5/4
z = -5/4
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