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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
(2*x-8)/x-4 = 0
(2*x-8)/x+(-4*x)/x = 0
2*x-4*x-8 = 0
-2*x-8 = 0
(-2*x-8)/x = 0
(-2*x-8)/x = 0 // * x
-2*x-8 = 0
-2*x-8 = 0 // + 8
-2*x = 8 // : -2
x = 8/(-2)
x = -4
x = -4
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