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D( x )
2*x^3-(28*x^2)-(30*x) = 0
2*x^3-(28*x^2)-(30*x) = 0
2*x^3-(28*x^2)-(30*x) = 0
2*x^3-28*x^2-30*x = 0
2*x^3-28*x^2-30*x = 0
2*x*(x^2-14*x-15) = 0
x^2-14*x-15 = 0
DELTA = (-14)^2-(-15*1*4)
DELTA = 256
DELTA > 0
x = (256^(1/2)+14)/(1*2) or x = (14-256^(1/2))/(1*2)
x = 15 or x = -1
2*x = 0
2*x = 0 // : 2
x = 0
x in (-oo:-1) U (-1:0) U (0:15) U (15:+oo)
(4*x^2-(56*x)-60)/(2*x^3-(28*x^2)-(30*x)) = 0
(4*x^2-56*x-60)/(2*x^3-28*x^2-30*x) = 0
4*x^2-56*x-60 = 0
4*(x^2-14*x-15) = 0
x^2-14*x-15 = 0
DELTA = (-14)^2-(-15*1*4)
DELTA = 256
DELTA > 0
x = (256^(1/2)+14)/(1*2) or x = (14-256^(1/2))/(1*2)
x = 15 or x = -1
4*(x+1)*(x-15) = 0
2*x^3-28*x^2-30*x = 0
2*x*(x^2-14*x-15) = 0
x^2-14*x-15 = 0
DELTA = (-14)^2-(-15*1*4)
DELTA = 256
DELTA > 0
x = (256^(1/2)+14)/(1*2) or x = (14-256^(1/2))/(1*2)
x = 15 or x = -1
2*x*(x+1)*(x-15) = 0
(4*(x+1)*(x-15))/(2*x*(x+1)*(x-15)) = 0
( x+1 )
x+1 = 0 // - 1
x = -1
( x-15 )
x-15 = 0 // + 15
x = 15
x in { -1}
x in { 15}
x belongs to the empty set
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