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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)
8/x+15/(x^2) = -1 // + 1
8/x+15/(x^2)+1 = 0
8*x^-1+15*x^-2+1 = 0
t_1 = x^-1
15*t_1^2+8*t_1^1+1 = 0
15*t_1^2+8*t_1+1 = 0
DELTA = 8^2-(1*4*15)
DELTA = 4
DELTA > 0
t_1 = (4^(1/2)-8)/(2*15) or t_1 = (-4^(1/2)-8)/(2*15)
t_1 = -1/5 or t_1 = -1/3
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 = -1/5
x^-1+1/5 = 0
1*x^-1 = -1/5 // : 1
x^-1 = -1/5
-1 < 0
1/(x^1) = -1/5 // * x^1
1 = -1/5*x^1 // : -1/5
-5 = x^1
x = -5
x in { -3, -5 }
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