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D( a )
a-2 = 0
a+1 = 0
a-2 = 0
a-2 = 0
a-2 = 0 // + 2
a = 2
a+1 = 0
a+1 = 0
a+1 = 0 // - 1
a = -1
a in (-oo:-1) U (-1:2) U (2:+oo)
2-(2/(a+1)) = a/(a-2) // - a/(a-2)
2-(2/(a+1))-(a/(a-2)) = 0
2-2*(a+1)^-1-(a/(a-2)) = 0
(-1*a)/(a-2)-2/(a+1)+2 = 0
(-2*(a-2))/((a+1)*(a-2))+(-1*a*(a+1))/((a+1)*(a-2))+(2*(a+1)*(a-2))/((a+1)*(a-2)) = 0
2*(a+1)*(a-2)-2*(a-2)-1*a*(a+1) = 0
2*a^2-a^2-3*a-2*a-4+4 = 0
a^2-5*a = 0
a^2-5*a = 0
a*(a-5) = 0
a-5 = 0 // + 5
a = 5
a*(a-5) = 0
(a*(a-5))/((a+1)*(a-2)) = 0
(a*(a-5))/((a+1)*(a-2)) = 0 // * (a+1)*(a-2)
a*(a-5) = 0
( a-5 )
a-5 = 0 // + 5
a = 5
( a )
a = 0
a in { 5, 0 }
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