Question

which transformation was used on abcd to result in abcd?○ translation 6 units up○ reflection across the x-axis○ rotation 180-degree (counterclockwise) about the origin○ reflection across the y-axis

Explanation:

First, identify a vertex of the original square ABCD, say (2,-1), and its corresponding vertex A'B'C'D' which is (2,1). Notice the x-coordinate stays the same, and the y-coordinate is multiplied by -1. This matches the rule for reflection across the x-axis, where a point (x,y) maps to (x,-y). Checking other vertices confirms this pattern holds.

Answer:

reflection across the x-axis