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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
(x-5)*(80/x-30) = 25 // - 25
(x-5)*(80/x-30)-25 = 0
(x-5)*(80*x^-1-30)-25 = 0
(x-5)*(80*x^-1-30)-25 = 0
205-30*x-400*x^-1 = 0
205-30*x-400*x^-1 = 0
5*(41-6*x-80*x^-1) = 0
41*x^0-6*x^1-80*x^-1 = 0
(41*x^1-6*x^2-80*x^0)/(x^1) = 0 // * x^2
x^1*(41*x^1-6*x^2-80*x^0) = 0
x^1
41*x-6*x^2-80 = 0
41*x-6*x^2-80 = 0
DELTA = 41^2-(-80*(-6)*4)
DELTA = -239
DELTA < 0
x in { }
5 = 0
5 = 0
5 = 0
x belongs to the empty set
x belongs to the empty set
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