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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
2*x-(12/x) = 5 // - 5
2*x-(12/x)-5 = 0
2*x-12*x^-1-5 = 0
2*x^1-12*x^-1-5*x^0 = 0
(2*x^2-5*x^1-12*x^0)/(x^1) = 0 // * x^2
x^1*(2*x^2-5*x^1-12*x^0) = 0
x^1
2*x^2-5*x-12 = 0
2*x^2-5*x-12 = 0
DELTA = (-5)^2-(-12*2*4)
DELTA = 121
DELTA > 0
x = (121^(1/2)+5)/(2*2) or x = (5-121^(1/2))/(2*2)
x = 4 or x = -3/2
x in { -3/2, 4}
x in { -3/2, 4 }
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