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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
1-(39.67/x) = 0.55 // - 0.55
1-(39.67/x)-0.55 = 0
1-39.67*x^-1-0.55 = 0
-39.67*x^-1 = -0.45 // : -39.67
x^-1 = 0.01134358
-1 < 0
1/(x^1) = 0.01134358 // * x^1
1 = 0.01134358*x^1 // : 0.01134358
88.15559109 = x^1
x = 88.15559109
x = 88.15559109
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