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D( n )
n = 0
n = 0
n = 0
n in (-oo:0) U (0:+oo)
8*n-(56/n)-7 = 0
8*n-56*n^-1-7 = 0
8*n^1-56*n^-1-7*n^0 = 0
(8*n^2-7*n^1-56*n^0)/(n^1) = 0 // * n^2
n^1*(8*n^2-7*n^1-56*n^0) = 0
n^1
8*n^2-7*n-56 = 0
8*n^2-7*n-56 = 0
DELTA = (-7)^2-(-56*4*8)
DELTA = 1841
DELTA > 0
n = (1841^(1/2)+7)/(2*8) or n = (7-1841^(1/2))/(2*8)
n = (1841^(1/2)+7)/16 or n = (7-1841^(1/2))/16
n in { (7-1841^(1/2))/16, (1841^(1/2)+7)/16}
n in { (7-1841^(1/2))/16, (1841^(1/2)+7)/16 }
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