Step by step
The question
Question: glide reflect the shape A(−2, 1), B(−1, 3) and C(0, 1): translate up 2, then reflect in the line x = 1.
1 Draw the shape
Put the points on the grid and join them.
The mirror line is the line x = 1.
A glide reflection is a slide along the mirror line, and a flip in it.
Like footprints in the sand: left, right, left.
Careful!
The mirror line is upright.
So the slide goes up or down, along it.
Any other slide is not a glide.
2 Slide
Up 2: y gets 2 bigger.
The rule: (x, y + 2).
A is (−2, 1): it goes to (−2, 3).
B goes to (−1, 5).
C goes to (0, 3).
Join them.
3 Flip
Flip in the line x = 1: count from the point to the line, then the same again on the other side.
A' is (−2, 3): it goes to (4, 3).
B' goes to (3, 5).
C' goes to (2, 3).
Join them: the final image.
So the image is A''(4, 3), B''(3, 5) and C''(2, 3).
4 Check
Let's check the other way round: flip first, then slide.
For a glide, it must give the same points.
The same points as before.
Right!
Let's look back.
First: draw the shape.
Then: slide.
Then: flip.
Last: check.