Which transformation will result in an image that is congruent to its pre-image?

Question

1. (x,y)→(-3x,y)
2. (x,y)→(3x,y-1)
3. (x,y)→(-x,y)
4. (x,y)→(-x,3y)

Answer 1

(x, y)→(-x,y) is reflection through the y-axis. In a reflection, the image and pre-image are congruent.