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x in (-oo:+oo)
x*((1000*x-3000)/1000) = 40/100 // - 40/100
x*((1000*x-3000)/1000)-(40/100) = 0
x*((1000*x-3000)/1000)-2/5 = 0
(x*(1000*x-3000))/1000-2/5 = 0
(5*x*(1000*x-3000))/(5*1000)+(-2*1000)/(5*1000) = 0
5*x*(1000*x-3000)-2*1000 = 0
5000*x^2-15000*x-2000 = 0
5000*x^2-15000*x-2000 = 0
1000*(5*x^2-15*x-2) = 0
5*x^2-15*x-2 = 0
DELTA = (-15)^2-(-2*4*5)
DELTA = 265
DELTA > 0
x = (265^(1/2)+15)/(2*5) or x = (15-265^(1/2))/(2*5)
x = (265^(1/2)+15)/10 or x = (15-265^(1/2))/10
1000*(x-((15-265^(1/2))/10))*(x-((265^(1/2)+15)/10)) = 0
(1000*(x-((15-265^(1/2))/10))*(x-((265^(1/2)+15)/10)))/(5*1000) = 0
(1000*(x-((15-265^(1/2))/10))*(x-((265^(1/2)+15)/10)))/(5*1000) = 0 // * 5*1000
1000*(x-((15-265^(1/2))/10))*(x-((265^(1/2)+15)/10)) = 0
( 1000 )
1000 = 0
x belongs to the empty set
( x-((15-265^(1/2))/10) )
x-((15-265^(1/2))/10) = 0 // + (15-265^(1/2))/10
x = (15-265^(1/2))/10
( x-((265^(1/2)+15)/10) )
x-((265^(1/2)+15)/10) = 0 // + (265^(1/2)+15)/10
x = (265^(1/2)+15)/10
x in { (15-265^(1/2))/10, (265^(1/2)+15)/10 }
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