Heyo another question on my exam for 20 points help me out

The table below represents a linear function f(x) and the equation represents a function g(x): x f(x) −1 −5 0 −1 1 3 g(x) g(x) = 2x − 7 part a: write a sentence to compare the slope of the two functions and show the steps you used to determine the slope of f(x) and g(x). (6 points) part b: which function has a greater y-intercept? justify your answer. (4 points)

Which geometric principle is used to justify the construction below?

How is this equation completed? i cannot find any examples in the book.