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D( x )
x = 0
x*x = 0
x = 0
x = 0
x*x = 0
x*x = 0
1*x^2 = 0 // : 1
x^2 = 0
x = 0
x in (-oo:0) U (0:+oo)
7/x+1/(x*x)+12 = 0
7*x^-1+x^-2+12 = 0
t_1 = x^-1
1*t_1^2+7*t_1^1+12 = 0
t_1^2+7*t_1+12 = 0
DELTA = 7^2-(1*4*12)
DELTA = 1
DELTA > 0
t_1 = (1^(1/2)-7)/(1*2) or t_1 = (-1^(1/2)-7)/(1*2)
t_1 = -3 or t_1 = -4
t_1 = -4
x^-1+4 = 0
1*x^-1 = -4 // : 1
x^-1 = -4
-1 < 0
1/(x^1) = -4 // * x^1
1 = -4*x^1 // : -4
-1/4 = x^1
x = -1/4
t_1 = -3
x^-1+3 = 0
1*x^-1 = -3 // : 1
x^-1 = -3
-1 < 0
1/(x^1) = -3 // * x^1
1 = -3*x^1 // : -3
-1/3 = x^1
x = -1/3
x in { -1/4, -1/3 }
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