The vertices of Figure ABCD are A(1,1), B(2,3) C(4,3) and D(5,1). If Figure ABCD is reflected over the line y = -1, find the coordinates of vertex B'.

Explanation:

The line y = -1 is horizontal: parallel to the y-axis.

The point B (2,3) is above the line y = - 1 at a distance equal to the y-coordinate of B (y = 3) less - 1:

When the point B (2,3) is reflected over the line y = -1, the x-coordinate does not change.  The image will be 4 units down the line y = -1, thus the y-coordinate will be - 1 - 4 = - 5.

Hence, the coordinates of the vertex B' are x = 2, y = - 5: (2, - 5).