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D( r )
r^2-r-12 = 0
r^2-r-12 = 0
r^2-r-12 = 0
r^2-r-12 = 0
DELTA = (-1)^2-(-12*1*4)
DELTA = 49
DELTA > 0
r = (49^(1/2)+1)/(1*2) or r = (1-49^(1/2))/(1*2)
r = 4 or r = -3
r in (-oo:-3) U (-3:4) U (4:+oo)
(r^2-r-6)/(r^2-r-12) = 0
r^2-r-6 = 0
r^2-r-6 = 0
DELTA = (-1)^2-(-6*1*4)
DELTA = 25
DELTA > 0
r = (25^(1/2)+1)/(1*2) or r = (1-25^(1/2))/(1*2)
r = 3 or r = -2
(r+2)*(r-3) = 0
r^2-r-12 = 0
r^2-r-12 = 0
DELTA = (-1)^2-(-12*1*4)
DELTA = 49
DELTA > 0
r = (49^(1/2)+1)/(1*2) or r = (1-49^(1/2))/(1*2)
r = 4 or r = -3
(r+3)*(r-4) = 0
((r+2)*(r-3))/((r+3)*(r-4)) = 0
( r+2 )
r+2 = 0 // - 2
r = -2
( r-3 )
r-3 = 0 // + 3
r = 3
r in { -2, 3 }
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