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x in (-oo:+oo)
2/3 = x*(30-x) // - x*(30-x)
2/3-(x*(30-x)) = 0
2/3-1*x*(30-x) = 0
(-1*3*x*(30-x))/3+2/3 = 0
2-1*3*x*(30-x) = 0
3*x^2-90*x+2 = 0
3*x^2-90*x+2 = 0
3*x^2-90*x+2 = 0
DELTA = (-90)^2-(2*3*4)
DELTA = 8076
DELTA > 0
x = (8076^(1/2)+90)/(2*3) or x = (90-8076^(1/2))/(2*3)
x = (2*2019^(1/2)+90)/6 or x = (90-2*2019^(1/2))/6
(x-((90-2*2019^(1/2))/6))*(x-((2*2019^(1/2)+90)/6)) = 0
((x-((90-2*2019^(1/2))/6))*(x-((2*2019^(1/2)+90)/6)))/3 = 0
((x-((90-2*2019^(1/2))/6))*(x-((2*2019^(1/2)+90)/6)))/3 = 0 // * 3
(x-((90-2*2019^(1/2))/6))*(x-((2*2019^(1/2)+90)/6)) = 0
( x-((2*2019^(1/2)+90)/6) )
x-((2*2019^(1/2)+90)/6) = 0 // + (2*2019^(1/2)+90)/6
x = (2*2019^(1/2)+90)/6
( x-((90-2*2019^(1/2))/6) )
x-((90-2*2019^(1/2))/6) = 0 // + (90-2*2019^(1/2))/6
x = (90-2*2019^(1/2))/6
x in { (2*2019^(1/2)+90)/6, (90-2*2019^(1/2))/6 }
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