Rewrite the inequality as:
\[ 2x + 4y = 9 \quad \text{(boundary line)}. \]
Test the origin \((0, 0)\) in the inequality:
\[ 2(0) + 4(0) \leq 9 \quad \text{True.} \]
Thus, the solution includes the origin. Since the inequality is \(\leq\), the boundary line is included, and the solution is the closed half-plane containing the origin.