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D( x )
x+3 = 0
x+3 = 0
x+3 = 0
x+3 = 0 // - 3
x = -3
x in (-oo:-3) U (-3:+oo)
(x^3-(5*x^2)-(31*x)-21)/(x+3) = 0
(x^3-5*x^2-31*x-21)/(x+3) = 0
x^3-5*x^2-31*x-21 = 0
x^3-5*x^2-31*x-21 = 0
{ 1, -1, 3, -3, 7, -7, 21, -21 }
1
x = 1
x^3-5*x^2-31*x-21 = -56
1
-1
x = -1
x^3-5*x^2-31*x-21 = 4
-1
3
x = 3
x^3-5*x^2-31*x-21 = -132
3
-3
x = -3
x^3-5*x^2-31*x-21 = 0
-3
x+3
x^2-8*x-7
x^3-5*x^2-31*x-21
x+3
-x^3-3*x^2
-8*x^2-31*x-21
8*x^2+24*x
-7*x-21
7*x+21
0
x^2-8*x-7 = 0
DELTA = (-8)^2-(-7*1*4)
DELTA = 92
DELTA > 0
x = (92^(1/2)+8)/(1*2) or x = (8-92^(1/2))/(1*2)
x = (2*23^(1/2)+8)/2 or x = (8-2*23^(1/2))/2
x in { (8-2*23^(1/2))/2, (2*23^(1/2)+8)/2, -3}
(x-((8-2*23^(1/2))/2))*(x-((2*23^(1/2)+8)/2))*(x+3) = 0
(x-((8-2*23^(1/2))/2))*(x-((2*23^(1/2)+8)/2)) = 0
( x-((2*23^(1/2)+8)/2) )
x-((2*23^(1/2)+8)/2) = 0 // + (2*23^(1/2)+8)/2
x = (2*23^(1/2)+8)/2
( x-((8-2*23^(1/2))/2) )
x-((8-2*23^(1/2))/2) = 0 // + (8-2*23^(1/2))/2
x = (8-2*23^(1/2))/2
x in { (2*23^(1/2)+8)/2, (8-2*23^(1/2))/2 }
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