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D( x )
x = 0
x^2 = 0
x = 0
x = 0
x^2 = 0
x^2 = 0
1*x^2 = 0 // : 1
x^2 = 0
x = 0
x in (-oo:0) U (0:+oo)
1-(1/x) = 12/(x^2) // - 12/(x^2)
1-(1/x)-(12/(x^2)) = 0
1-x^-1-12*x^-2 = 0
t_1 = x^-1
1-12*t_1^2-1*t_1^1 = 0
1-12*t_1^2-t_1 = 0
DELTA = (-1)^2-(-12*1*4)
DELTA = 49
DELTA > 0
t_1 = (49^(1/2)+1)/(-12*2) or t_1 = (1-49^(1/2))/(-12*2)
t_1 = -1/3 or t_1 = 1/4
t_1 = -1/3
x^-1+1/3 = 0
1*x^-1 = -1/3 // : 1
x^-1 = -1/3
-1 < 0
1/(x^1) = -1/3 // * x^1
1 = -1/3*x^1 // : -1/3
-3 = x^1
x = -3
t_1 = 1/4
x^-1-1/4 = 0
1*x^-1 = 1/4 // : 1
x^-1 = 1/4
-1 < 0
1/(x^1) = 1/4 // * x^1
1 = 1/4*x^1 // : 1/4
4 = x^1
x = 4
x in { -3, 4 }
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