Solution

$ 9x^2 - 18|x| + 5 = 0 $

Let $ y = |x| \Rightarrow x^2 = y^2 $

So equation becomes:
$ 9y^2 - 18y + 5 = 0 $

Solve:
$ y = \frac{18 \pm \sqrt{324 - 180}}{18} = \frac{18 \pm \sqrt{144}}{18} = \frac{18 \pm 12}{18} $

So,
$ y = \frac{30}{18} = \frac{5}{3},\quad y = \frac{6}{18} = \frac{1}{3} $

Since $ y = |x| $,

Roots:
$ x = \pm \frac{5}{3},\ \pm \frac{1}{3} $

Product of all roots:
$ \left(\frac{5}{3}\right)\left(-\frac{5}{3}\right)\left(\frac{1}{3}\right)\left(-\frac{1}{3}\right) $

$ = \frac{25}{9} \cdot \frac{1}{9} = \frac{25}{81} $