1. **State the problem:** Expand the expression $x(x + 4)$. 2. **Recall the distributive property:** To expand, multiply $x$ by each term inside the parentheses: $$x(x + 4) = x \cdot x + x \cdot 4$$ 3. **Perform the multiplication:** $$x \cdot x = x^2$$ $$x \cdot 4 = 4x$$ 4. **Combine the results:** $$x(x + 4) = x^2 + 4x$$ 5. **Final answer:** The expanded form of $x(x + 4)$ is $$\boxed{x^2 + 4x}$$