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D( n )
12*n+30 = 0
12*n^4-(21*n^3) = 0
12*n+30 = 0
12*n+30 = 0
12*n+30 = 0 // - 30
12*n = -30 // : 12
n = -30/12
n = -5/2
12*n^4-(21*n^3) = 0
12*n^4-(21*n^3) = 0
12*n^4-21*n^3 = 0
12*n^4-21*n^3 = 0
3*n^3*(4*n-7) = 0
4*n-7 = 0 // + 7
4*n = 7 // : 4
n = 7/4
3*n^3 = 0
3*n^3 = 0 // : 3
n^3 = 0
n = 0
n in (-oo:-5/2) U (-5/2:0) U (0:7/4) U (7/4:+oo)
((2*n^2+5*n)/(12*n^4-(21*n^3)))*((6*n)/(12*n+30)) = 0
((2*n^2+5*n)/(12*n^4-21*n^3))*((6*n)/(12*n+30)) = 0
(6*n*(2*n^2+5*n))/((12*n^4-21*n^3)*(12*n+30)) = 0
2*n^2+5*n = 0
n*(2*n+5) = 0
2*n+5 = 0 // - 5
2*n = -5 // : 2
n = -5/2
n*(n+5/2) = 0
12*n^4-21*n^3 = 0
3*n^3*(4*n-7) = 0
4*n-7 = 0 // + 7
4*n = 7 // : 4
n = 7/4
3*n^3*(n-7/4) = 0
(6*n*n*(n+5/2))/(3*n^3*(n-7/4)*(12*n+30)) = 0
( 6*n )
6*n = 0 // : 6
n = 0
( n+5/2 )
n+5/2 = 0 // - 5/2
n = -5/2
( n )
n = 0
n in { 0}
n in { -5/2}
n in { 0}
n belongs to the empty set
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