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D( x )
20*x^2-((18/40)*x^2)-(37*x)-(90*x) = 0
20*x^2-((18/40)*x^2)-(37*x)-(90*x) = 0
20*x^2-((18/40)*x^2)-(37*x)-(90*x) = 0
20*x^2+(-9/20)*x^2-37*x-90*x = 0
391/20*x^2-127*x = 0
DELTA = (-127)^2-(0*4*391/20)
DELTA = 16129
DELTA > 0
x = (16129^(1/2)+127)/(2*391/20) or x = (127-16129^(1/2))/(2*391/20)
x = 2540/391 or x = 0
x in (-oo:0) U (0:2540/391) U (2540/391:+oo)
(25*x^2-((4/25)*x))/(20*x^2-((18/40)*x^2)-(37*x)-(90*x)) = 0
(25*x^2+(-4/25)*x)/(20*x^2+(-9/20)*x^2-37*x-90*x) = 0
(25*x^2-4/25*x)/(391/20*x^2-127*x) = 0
25*x^2-4/25*x = 0
x*(25*x-4/25) = 0
25*x-4/25 = 0 // + 4/25
25*x = 4/25 // : 25
x = 4/25/25
x = 4/625
x*(x-4/625) = 0
391/20*x^2-127*x = 0
x*(391/20*x-127) = 0
391/20*x-127 = 0 // + 127
391/20*x = 127 // : 391/20
x = 127/391/20
x = 2540/391
x*(x-2540/391) = 0
(x*(x-4/625))/(x*(x-2540/391)) = 0
( x-4/625 )
x-4/625 = 0 // + 4/625
x = 4/625
( x )
x = 0
x in { 0}
x = 4/625
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