Question 180269
x^6-3x^3-18=0

(x^3-6)(x^3+3) = 0

x^3 = 6 or x^3 = -3

x= cbrt(6) or x = cbrt(-3)
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Note: There are 4 complex roots. You would have
to use DeMoire to find those.
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Cheers,
Stan H.