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n in (-oo:+oo)
306 = (n/2)*(3*3*n+2*9) // - (n/2)*(3*3*n+2*9)
306-((n/2)*(3*3*n+2*9)) = 0
306-1*1/2*n*(9*n+18) = 0
306-1*1/2*n*(9*n+18) = 0
306-9/2*n^2-9*n = 0
306-9/2*n^2-9*n = 0
9*(34-1/2*n^2-n) = 0
34-1/2*n^2-n = 0
DELTA = (-1)^2-(-1/2*4*34)
DELTA = 69
DELTA > 0
n = (69^(1/2)+1)/(-1/2*2) or n = (1-69^(1/2))/(-1/2*2)
n = -(69^(1/2)+1) or n = 69^(1/2)-1
9*(n+69^(1/2)+1)*(n-69^(1/2)+1) = 0
9*(n+69^(1/2)+1)*(n-69^(1/2)+1) = 0
( n+69^(1/2)+1 )
n+69^(1/2)+1 = 0 // - 69^(1/2)+1
n = -(69^(1/2)+1)
( n-69^(1/2)+1 )
n-69^(1/2)+1 = 0 // - 1-69^(1/2)
n = -(1-69^(1/2))
n = 69^(1/2)-1
n in { -(69^(1/2)+1), 69^(1/2)-1 }
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