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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
12-(4*x) = 1/x // - 1/x
12-(4*x)-(1/x) = 0
12-4*x-x^-1 = 0
12*x^0-4*x^1-1*x^-1 = 0
(12*x^1-4*x^2-1*x^0)/(x^1) = 0 // * x^2
x^1*(12*x^1-4*x^2-1*x^0) = 0
x^1
12*x-4*x^2-1 = 0
12*x-4*x^2-1 = 0
DELTA = 12^2-(-4*(-1)*4)
DELTA = 128
DELTA > 0
x = (128^(1/2)-12)/(-4*2) or x = (-128^(1/2)-12)/(-4*2)
x = (8*2^(1/2)-12)/(-8) or x = (-8*2^(1/2)-12)/(-8)
x in { (8*2^(1/2)-12)/(-8), (-8*2^(1/2)-12)/(-8)}
x in { (8*2^(1/2)-12)/(-8), (-8*2^(1/2)-12)/(-8) }
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