Решим неравенство методом интервалов.
$$ (x-4)(x-6) = 0 $$
$$ x-4 = 0 $$ или $$ x-6 = 0 $$
$$ x_1 = 4, x_2 = 6 $$
+ - +
----(4)-----(6)-----
$$ x \in (-\infty; 4) \cup (6; +\infty) $$
Ответ: $$ x \in (-\infty; 4) \cup (6; +\infty) $$