C2 Week-1 Help with approximation of derivatives graph

Course Q&A Math for Machine Learning Calculus for Machine Learning and Data Science
1

Hi,
I don’t understand what we see in this graph:
How is delta x calculated, based on which points?

image
image1754×644 57.7 KB

thanks

2

Delta x is the difference in the x axis between the point X value and the X value = 3 i.e. Xpoint - 3 = delta X.