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D( y )
y = 0
y^2 = 0
y = 0
y = 0
y^2 = 0
y^2 = 0
1*y^2 = 0 // : 1
y^2 = 0
y = 0
y in (-oo:0) U (0:+oo)
(4*y)/y-(12/y)-3-3 = 72/(y^2)-9 // - 72/(y^2)-9
(4*y)/y-(12/y)-(72/(y^2))-3-3+9 = 0
(4*y)/y-12*y^-1-72*y^-2-3-3+9 = 0
7-12*y^-1-72*y^-2 = 0
t_1 = y^-1
7-72*t_1^2-12*t_1^1 = 0
7-72*t_1^2-12*t_1 = 0
DELTA = (-12)^2-(-72*4*7)
DELTA = 2160
DELTA > 0
t_1 = (2160^(1/2)+12)/(-72*2) or t_1 = (12-2160^(1/2))/(-72*2)
t_1 = (12*15^(1/2)+12)/(-144) or t_1 = (12-12*15^(1/2))/(-144)
t_1 = (12*15^(1/2)+12)/(-144)
y^-1-((12*15^(1/2)+12)/(-144)) = 0
1*y^-1 = (12*15^(1/2)+12)/(-144) // : 1
y^-1 = (12*15^(1/2)+12)/(-144)
-1 < 0
1/(y^1) = (12*15^(1/2)+12)/(-144) // * y^1
1 = ((12*15^(1/2)+12)/(-144))*y^1 // : (12*15^(1/2)+12)/(-144)
-144*(12*15^(1/2)+12)^-1 = y^1
y = -144*(12*15^(1/2)+12)^-1
t_1 = (12-12*15^(1/2))/(-144)
y^-1-((12-12*15^(1/2))/(-144)) = 0
1*y^-1 = (12-12*15^(1/2))/(-144) // : 1
y^-1 = (12-12*15^(1/2))/(-144)
-1 < 0
1/(y^1) = (12-12*15^(1/2))/(-144) // * y^1
1 = ((12-12*15^(1/2))/(-144))*y^1 // : (12-12*15^(1/2))/(-144)
-144*(12-12*15^(1/2))^-1 = y^1
y = -144*(12-12*15^(1/2))^-1
y in { -144*(12*15^(1/2)+12)^-1, -144*(12-12*15^(1/2))^-1 }
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