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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)
(7*x)/x-(21/x)-3-3 = 126/(x^2)-9 // - 126/(x^2)-9
(7*x)/x-(21/x)-(126/(x^2))-3-3+9 = 0
(7*x)/x-21*x^-1-126*x^-2-3-3+9 = 0
10-21*x^-1-126*x^-2 = 0
t_1 = x^-1
10-126*t_1^2-21*t_1^1 = 0
10-126*t_1^2-21*t_1 = 0
DELTA = (-21)^2-(-126*4*10)
DELTA = 5481
DELTA > 0
t_1 = (5481^(1/2)+21)/(-126*2) or t_1 = (21-5481^(1/2))/(-126*2)
t_1 = (3*609^(1/2)+21)/(-252) or t_1 = (21-3*609^(1/2))/(-252)
t_1 = (3*609^(1/2)+21)/(-252)
x^-1-((3*609^(1/2)+21)/(-252)) = 0
1*x^-1 = (3*609^(1/2)+21)/(-252) // : 1
x^-1 = (3*609^(1/2)+21)/(-252)
-1 < 0
1/(x^1) = (3*609^(1/2)+21)/(-252) // * x^1
1 = ((3*609^(1/2)+21)/(-252))*x^1 // : (3*609^(1/2)+21)/(-252)
-252*(3*609^(1/2)+21)^-1 = x^1
x = -252*(3*609^(1/2)+21)^-1
t_1 = (21-3*609^(1/2))/(-252)
x^-1-((21-3*609^(1/2))/(-252)) = 0
1*x^-1 = (21-3*609^(1/2))/(-252) // : 1
x^-1 = (21-3*609^(1/2))/(-252)
-1 < 0
1/(x^1) = (21-3*609^(1/2))/(-252) // * x^1
1 = ((21-3*609^(1/2))/(-252))*x^1 // : (21-3*609^(1/2))/(-252)
-252*(21-3*609^(1/2))^-1 = x^1
x = -252*(21-3*609^(1/2))^-1
x in { -252*(3*609^(1/2)+21)^-1, -252*(21-3*609^(1/2))^-1 }
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