Answer
See graph.
$(-\infty,\infty)$, $[-2,6]$.
Work Step by Step
Step 1. See graph for $y=2-4cos(3x)$ with key points or transform from $y=cos(x)$ (shrink horizontally by a factor of $1/3$, stretch vertically by a factor of 4, reflect across the x-axis, then shift 2 units up.)
Step 2. Based on the graph, we can determine the domain as $(-\infty,\infty)$ range as $[-2,6]$.
