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x in (-oo:+oo)
y = (-1/15)*(2*x+1)*(2*x-15) // - (-1/15)*(2*x+1)*(2*x-15)
y-((-1/15)*(2*x+1)*(2*x-15)) = 0
(1/15)*(2*x-15)*(2*x+1)+y = 0
1/15*(2*x-15)*(2*x+1)+y = 0
1/15*(2*x-15)*(2*x+1)+y = 0
4/15*x^2-28/15*x+y-1 = 0
4/15*x^2-28/15*x+y-1 = 0
4/15*x^2-28/15*x+y-1 = 0
DELTA = (-28/15)^2-(4/15*4*(y-1))
DELTA = 784/225-16/15*(y-1)
784/225-16/15*(y-1) = 0
(-16/15*225*(y-1))/225+784/225 = 0
784-16/15*225*(y-1) = 0
1024-240*y = 0
(1024-240*y)/225 = 0
(1024-240*y)/225 = 0 // * 225
1024-240*y = 0
1024-240*y = 0 // - 1024
-240*y = -1024 // : -240
y = -1024/(-240)
y = 64/15
DELTA = 0 <=> t_3 = 64/15
x = 28/15/(4/15*2) i y = 64/15
x = 7/2 i y = 64/15
( x = ((784/225-16/15*(y-1))^(1/2)+28/15)/(4/15*2) or x = (28/15-(784/225-16/15*(y-1))^(1/2))/(4/15*2) ) i y > 64/15
( x = 15/8*((784/225-16/15*(y-1))^(1/2)+28/15) or x = 15/8*(28/15-(784/225-16/15*(y-1))^(1/2)) ) i y > 64/15
y-64/15 > 0
y-64/15 > 0 // + 64/15
y > 64/15
x in { 7/2, 15/8*((784/225-16/15*(y-1))^(1/2)+28/15), 15/8*(28/15-(784/225-16/15*(y-1))^(1/2)) }
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