Notes
When we perform a transformation on an object, every point in the original object gets a partner point in the second object.
The original object we call the pre-image.
The new object we call the image.
To help us know which points are partners we use very similar names. We use a capital letter for the point in the pre-image and the SAME capital letter with a ' mark for the point in the image.
For example if A (read as "point A") is in the pre-image, then A' (read as "point A prime") will be its partner in the image.