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x in (-oo:+oo)
Y = (-2/5)*(x-2)*(x-15) // - (-2/5)*(x-2)*(x-15)
Y-((-2/5)*(x-2)*(x-15)) = 0
(2/5)*(x-2)*(x-15)+Y = 0
2/5*(x-2)*(x-15)+Y = 0
2/5*(x-2)*(x-15)+Y = 0
Y+2/5*x^2-34/5*x+12 = 0
Y+2/5*x^2-34/5*x+12 = 0
Y+2/5*x^2-34/5*x+12 = 0
DELTA = (-34/5)^2-(2/5*4*(Y+12))
DELTA = 1156/25-8/5*(Y+12)
1156/25-8/5*(Y+12) = 0
(-8/5*25*(Y+12))/25+1156/25 = 0
1156-8/5*25*(Y+12) = 0
676-40*Y = 0
(676-40*Y)/25 = 0
(676-40*Y)/25 = 0 // * 25
676-40*Y = 0
676-40*Y = 0 // - 676
-40*Y = -676 // : -40
Y = -676/(-40)
Y = 169/10
DELTA = 0 <=> t_3 = 169/10
x = 34/5/(2/5*2) i Y = 169/10
x = 17/2 i Y = 169/10
( x = ((1156/25-8/5*(Y+12))^(1/2)+34/5)/(2/5*2) or x = (34/5-(1156/25-8/5*(Y+12))^(1/2))/(2/5*2) ) i Y > 169/10
( x = 5/4*((1156/25-8/5*(Y+12))^(1/2)+34/5) or x = 5/4*(34/5-(1156/25-8/5*(Y+12))^(1/2)) ) i Y > 169/10
Y-169/10 > 0
Y-169/10 > 0 // + 169/10
Y > 169/10
x in { 17/2, 5/4*((1156/25-8/5*(Y+12))^(1/2)+34/5), 5/4*(34/5-(1156/25-8/5*(Y+12))^(1/2)) }
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