How do I add chart points together?

Question

In this video, two points on a chart are added together. As each individual point has X and Y values, how is addition performed?

I've researched 'adding chart points' and variations thereof but not found anything.

Answer 1

This is how points on elliptic curves are added. You can google "addition on elliptic curves" to get many explanations. This may also help: http://www.math.vt.edu/people/brown/class_homepages/elliptic_curve_addition.pdf

Answer 2

My students used to have trouble with this idea too, and it came down to this: you don't add the x-values of the point, you just add the y-values.

That's really all you need to know, but if you want to think more deeply, this goes back to how functions are designed. All that the x-value tells us is where we are looking on the graph. The x-axis itself is more of a locater than anything else. The y-values are what we are interested in, as long as we keep in mind which x-value they are located at.

Once you understand this idea the more detailed explanations will make more sense.