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D( x )
x+12 = 0
x+12 = 0
x+12 = 0
x+12 = 0 // - 12
x = -12
x in (-oo:-12) U (-12:+oo)
(650*x)/(x+12) = 311 // - 311
(650*x)/(x+12)-311 = 0
(650*x)/(x+12)+(-311*(x+12))/(x+12) = 0
650*x-311*(x+12) = 0
339*x-3732 = 0
(339*x-3732)/(x+12) = 0
(339*x-3732)/(x+12) = 0 // * x+12
339*x-3732 = 0
339*x-3732 = 0 // + 3732
339*x = 3732 // : 339
x = 3732/339
x = 1244/113
x = 1244/113
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