Consider the line with these parametric equations:
$x = -9t - 4$
$y = 9t - 2$
$z = -5t - 1$.
One set of symmetric equations for this line is
$\frac{x + 4}{9} = \frac{y - y_0}{b} = \frac{z - z_0}{c}$,
where $y_0 = -2$, $z_0 = -1$, $b = 9$, and $c = -5$.
Another set of symmetric equations for this line is
$\frac{x + 4}{9} = \frac{y - y_1}{b} = \frac{z - z_1}{c}$,
where $y_1 = -6$, $z_1 = -\frac{5}{9}$, $b = -9$, and $c = 5$
