Question

On a coordinate plane, a triangle has points A prime (negative 2, 10), B prime (negative 6, 4), and (negative 10, 8).
What is the pre-image of vertex A' if the image shown on the graph was created by a reflection across the line y = x?

(10, –2)
(–10, 2)
(–2, –10)
(2, 10)

Answer 1

Reflection across the line y = x swaps coordinates: (x, y) ↔ (y, x).
Since A' = (−2, 10) = (y, x), the pre-image is (10, −2).