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D( r )
r^2 = 0
r^2 = 0
r^2 = 0
1*r^2 = 0 // : 1
r^2 = 0
r = 0
r in (-oo:0) U (0:+oo)
r^2-r+r-(6/(r^2))-12 = 0
r^2-r+r-6*r^-2-12 = 0
r^2-6*r^-2-12 = 0
t_1 = r^2
1*t_1^1-6*t_1^-1-12 = 0
1*t_1^1-6*t_1^-1-12*t_1^0 = 0
(1*t_1^2-12*t_1^1-6*t_1^0)/(t_1^1) = 0 // * t_1^2
t_1^1*(1*t_1^2-12*t_1^1-6*t_1^0) = 0
t_1^1
t_1^2-12*t_1-6 = 0
t_1^2-12*t_1-6 = 0
DELTA = (-12)^2-(-6*1*4)
DELTA = 168
DELTA > 0
t_1 = (168^(1/2)+12)/(1*2) or t_1 = (12-168^(1/2))/(1*2)
t_1 = (2*42^(1/2)+12)/2 or t_1 = (12-2*42^(1/2))/2
t_1 in { (12-2*42^(1/2))/2, (2*42^(1/2)+12)/2}
t_1 = (12-2*42^(1/2))/2
r^2-((12-2*42^(1/2))/2) = 0
1*r^2 = (12-2*42^(1/2))/2 // : 1
r^2 = (12-2*42^(1/2))/2
t_1 = (2*42^(1/2)+12)/2
r^2-((2*42^(1/2)+12)/2) = 0
1*r^2 = (2*42^(1/2)+12)/2 // : 1
r^2 = (2*42^(1/2)+12)/2
r^2 = (2*42^(1/2)+12)/2 // ^ 1/2
abs(r) = ((2*42^(1/2)+12)^(1/2))/(2^(1/2))
r = ((2*42^(1/2)+12)^(1/2))/(2^(1/2)) or r = -(((2*42^(1/2)+12)^(1/2))/(2^(1/2)))
r in { ((2*42^(1/2)+12)^(1/2))/(2^(1/2)), -(((2*42^(1/2)+12)^(1/2))/(2^(1/2))) }
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