\(\sqrt{-x} = (-3x)^3\\ \sqrt{-x} = -27x^3\\ -x = 729x^3\\ 729x^3+x = 0\\ x(729x^2 + 1) = 0\\ x = 0 \text{ or }x^2 = -\dfrac{1}{729}\\ x^2 + \dfrac{1}{729}=0\\ x = \dfrac{\pm\sqrt{0^2-4(1)(1/729)}}{2}\\ x = \dfrac{1}{27}i\text{ or }x=-\dfrac{1}{27}i\text{ or }x = 0\)
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