$\frac{5}{7}x^9 - \frac{3}{14}x^9 - 1\frac{1}{2}x^9 = -1$
$\frac{10}{14}x^9 - \frac{3}{14}x^9 - 1\frac{7}{14}x^9 = -1$
$-x^9 = -1$
$x^9 = 1$
x = 1