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a in (-oo:+oo)
a*((a+4)/3)-(a*((2-(4*a))/6)) = 0
a*((a+4)/3)-(a*((2-4*a)/6)) = 0
(a*(a+4))/3+(-1*a*(2-4*a))/6 = 0
(6*a*(a+4))/(3*6)+(-1*3*a*(2-4*a))/(3*6) = 0
6*a*(a+4)-1*3*a*(2-4*a) = 0
18*a^2+18*a = 0
18*a^2+18*a = 0
18*a*(a+1) = 0
a+1 = 0 // - 1
a = -1
18*a*(a+1) = 0
(18*a*(a+1))/(3*6) = 0
(18*a*(a+1))/(3*6) = 0 // * 3*6
18*a*(a+1) = 0
( 18*a )
18*a = 0 // : 18
a = 0
( a+1 )
a+1 = 0 // - 1
a = -1
a in { 0, -1 }
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