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D( u )
u^2+10*u+21 = 0
u^2+10*u+21 = 0
u^2+10*u+21 = 0
u^2+10*u+21 = 0
DELTA = 10^2-(1*4*21)
DELTA = 16
DELTA > 0
u = (16^(1/2)-10)/(1*2) or u = (-16^(1/2)-10)/(1*2)
u = -3 or u = -7
u in (-oo:-7) U (-7:-3) U (-3:+oo)
(4*u^2+16*u+12)/(u^2+10*u+21) = 0
4*u^2+16*u+12 = 0
4*(u^2+4*u+3) = 0
u^2+4*u+3 = 0
DELTA = 4^2-(1*3*4)
DELTA = 4
DELTA > 0
u = (4^(1/2)-4)/(1*2) or u = (-4^(1/2)-4)/(1*2)
u = -1 or u = -3
4*(u+3)*(u+1) = 0
u^2+10*u+21 = 0
u^2+10*u+21 = 0
DELTA = 10^2-(1*4*21)
DELTA = 16
DELTA > 0
u = (16^(1/2)-10)/(1*2) or u = (-16^(1/2)-10)/(1*2)
u = -3 or u = -7
(u+7)*(u+3) = 0
(4*(u+3)*(u+1))/((u+7)*(u+3)) = 0
( u+1 )
u+1 = 0 // - 1
u = -1
( u+3 )
u+3 = 0 // - 3
u = -3
u in { -3}
u = -1
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