My textbook treats quadratic functions in vertex form as an extension to solving quadratic equations by completing the square. I just put together two lessons with guided examples and worksheets to go along that I am sharing. The thought process is 1st recognizing vertex form and putting equations in vertex form followed by graphing in vertex form and relating everything back to the parent function y = x^2.
Here is the 2nd worksheet to go with the parent graphs and vertex form examples.
I could only attach 3 files to the original posting.