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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) = 217 // - 217
(650*x)/(x+12)-217 = 0
(650*x)/(x+12)+(-217*(x+12))/(x+12) = 0
650*x-217*(x+12) = 0
433*x-2604 = 0
(433*x-2604)/(x+12) = 0
(433*x-2604)/(x+12) = 0 // * x+12
433*x-2604 = 0
433*x-2604 = 0 // + 2604
433*x = 2604 // : 433
x = 2604/433
x = 2604/433
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