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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
0.9/x = 100/1000 // - 100/1000
0.9/x-(100/1000) = 0
0.9/x-1/10 = 0
0.9*x^-1 = 1/10 // : 0.9
x^-1 = 0.11111111
-1 < 0
1/(x^1) = 0.11111111 // * x^1
1 = 0.11111111*x^1 // : 0.11111111
9.00000009 = x^1
x = 9.00000009
x = 9.00000009
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