[tex] \frac{x-1}{x} = \frac{3}{1} [/tex] ⇔ x-1 = 3x
-1 = 3x-x
-1 = 2x
x = - 1/2
[tex] \frac{x^{3}-1}{x^{3} } = \frac{-( \frac{1}{2})^{3} -1 }{-( \frac{1}{2})^{3}} = \frac{ -\frac{1}{8}- \frac{8}{8} }{- \frac{1}{8} } = \frac{- \frac{9}{8} }{- \frac{1}{8} } =- \frac{9}{8} ori - \frac{8}{1} = 9[/tex]