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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
3/x = x/7 // - x/7
3/x-(x/7) = 0
3*x^-1-1/7*x^1 = 0
(3*x^0-1/7*x^2)/(x^1) = 0 // * x^2
x^1*(3*x^0-1/7*x^2) = 0
x^1
(-1/7)*x^2+3 = 0
(-1/7)*x^2+3 = 0
DELTA = 0^2-(3*4*(-1/7))
DELTA = 12/7
DELTA > 0
x = ((12/7)^(1/2)+0)/(2*(-1/7)) or x = (0-(12/7)^(1/2))/(2*(-1/7))
x = -7/2*(12/7)^(1/2) or x = 7/2*(12/7)^(1/2)
x in { -7/2*(12/7)^(1/2), 7/2*(12/7)^(1/2)}
x in { -7/2*(12/7)^(1/2), 7/2*(12/7)^(1/2) }
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