To reflect a rectangle over the line $y = 0$, you need to flip its coordinates across the x-axis.

Reflecting a rectangle over the line $y = 0$ entails inverting it over the x-axis. This line, $y = 0$, is commonly referred to as the x-axis. When you perform a reflection over this line, you change the sign of the y-coordinates of all the rectangle’s vertices, while the x-coordinates remain unchanged.

Consider a rectangle defined by its vertices at $(x_1, y_1)$, $(x_2, y_2)$, $(x_3, y_3)$, and $(x_4, y_4)$. To reflect this rectangle over the line $y = 0$, you will transform each vertex as follows: $(x_1, -y_1), \quad (x_2, -y_2), \quad (x_3, -y_3), \quad (x_4, -y_4).$ This transformation effectively involves taking each y-coordinate and multiplying it by $-1$.

For instance, if your rectangle has vertices at $(2, 3)$, $(5, 3)$, $(5, 1)$, and $(2, 1)$, reflecting it over the line $y = 0$ results in new vertices at: $(2, -3), \quad (5, -3), \quad (5, -1), \quad (2, -1).$ As you can see, only the y-coordinates have been altered, effectively flipping the rectangle upside down across the x-axis.

This reflection method applies to any rectangle, regardless of its position in the coordinate plane. By mastering this straightforward transformation, you will be equipped to easily reflect any shape over the x-axis, a fundamental skill in coordinate geometry.