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D( y )
y = 0
y = 0
y = 0
y in (-oo:0) U (0:+oo)
(6*y)/y-8+3 = y-(40/y)+8 // - y-(40/y)+8
40/y-y+(6*y)/y-8-8+3 = 0
40*y^-1-1*y^1-7*y^0 = 0
(40*y^0-1*y^2-7*y^1)/(y^1) = 0 // * y^2
y^1*(40*y^0-1*y^2-7*y^1) = 0
y^1
40-y^2-7*y = 0
40-y^2-7*y = 0
DELTA = (-7)^2-(-1*4*40)
DELTA = 209
DELTA > 0
y = (209^(1/2)+7)/(-1*2) or y = (7-209^(1/2))/(-1*2)
y = (209^(1/2)+7)/(-2) or y = (7-209^(1/2))/(-2)
y in { (209^(1/2)+7)/(-2), (7-209^(1/2))/(-2)}
y in { (209^(1/2)+7)/(-2), (7-209^(1/2))/(-2) }
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