What is the equation for the line of reflection that maps the trapezoid onto itself?

If you have a URL for the pic, you can just include it in the post.....we will be able to access it

If not....

1st.....you must have the image saved on your hard drive....I use the Snipping Tool  for this

2nd......click on the "Image" icon above

3rd....hit the "upload tab"

4th....choose the file you wish to upload.....hit  "open"

5th.....hit the "upload" tab......you might be asked to verify  some  "Captcha" images

Here it is https://static.k12.com/nextgen_media/assets/8080857-NG_GMT_SemA_IT_01_30.png

x  =  -2

To see this......imagine that we rotate [ "spin" ] the trapezoid about this line......it maps the trapezoid back to its original image