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D( x )
x^2 = 0
x^2 = 0
x^2 = 0
1*x^2 = 0 // : 1
x^2 = 0
x = 0
x in (-oo:0) U (0:+oo)
x^2*(((3*x+(7*x)/(x^2)-28)*(3*x-12))/28) = 0
(x^2*(3*x+7*x^-1-28)*(3*x-12))/28 = 0
3*x+7*x^-1-28 = 0
3*x^1+7*x^-1-28*x^0 = 0
(3*x^2-28*x^1+7*x^0)/(x^1) = 0 // * x^2
x^1*(3*x^2-28*x^1+7*x^0) = 0
x^1
3*x^2-28*x+7 = 0
3*x^2-28*x+7 = 0
DELTA = (-28)^2-(3*4*7)
DELTA = 700
DELTA > 0
x = (700^(1/2)+28)/(2*3) or x = (28-700^(1/2))/(2*3)
x = (10*7^(1/2)+28)/6 or x = (28-10*7^(1/2))/6
x in { (28-10*7^(1/2))/6, (10*7^(1/2)+28)/6}
(x-((28-10*7^(1/2))/6))*(x-((10*7^(1/2)+28)/6)) = 0
(x^2*(x-((28-10*7^(1/2))/6))*(x-((10*7^(1/2)+28)/6))*(3*x-12))/28 = 0
( 3*x-12 )
3*x-12 = 0 // + 12
3*x = 12 // : 3
x = 12/3
x = 4
( x-((10*7^(1/2)+28)/6) )
x-((10*7^(1/2)+28)/6) = 0 // + (10*7^(1/2)+28)/6
x = (10*7^(1/2)+28)/6
( x-((28-10*7^(1/2))/6) )
x-((28-10*7^(1/2))/6) = 0 // + (28-10*7^(1/2))/6
x = (28-10*7^(1/2))/6
( x^2 )
1*x^2 = 0 // : 1
x^2 = 0
x = 0
x in { 0}
x in { 4, (10*7^(1/2)+28)/6, (28-10*7^(1/2))/6 }
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