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D( x )
x+13 = 0
x+13 = 0
x+13 = 0
x+13 = 0 // - 13
x = -13
x in (-oo:-13) U (-13:+oo)
x/(x+13) = 0.125 // - 0.125
x/(x+13)-0.125 = 0
x/(x+13)+(-0.125*(x+13))/(x+13) = 0
x-0.125*(x+13) = 0
0.875*x-1.625 = 0
(0.875*x-1.625)/(x+13) = 0
(0.875*x-1.625)/(x+13) = 0 // * x+13
0.875*x-1.625 = 0
0.875*x-1.625 = 0 // + 1.625
0.875*x = 1.625 // : 0.875
x = 1.625/0.875
x = 1.85714286
x = 1.85714286
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