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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-(9/x)-(36/(x^2)) = 0
1-9*x^-1-36*x^-2 = 0
t_1 = x^-1
1-36*t_1^2-9*t_1^1 = 0
1-36*t_1^2-9*t_1 = 0
DELTA = (-9)^2-(-36*1*4)
DELTA = 225
DELTA > 0
t_1 = (225^(1/2)+9)/(-36*2) or t_1 = (9-225^(1/2))/(-36*2)
t_1 = -1/3 or t_1 = 1/12
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 = 1/12
x^-1-1/12 = 0
1*x^-1 = 1/12 // : 1
x^-1 = 1/12
-1 < 0
1/(x^1) = 1/12 // * x^1
1 = 1/12*x^1 // : 1/12
12 = x^1
x = 12
x in { -3, 12 }
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