Question

Can the graph of a function be a horizontal line? A vertical line? Explain.

Answer 1

It can be a function if it's horizontal because it's only touching each point once, it can't be a function for a vertical line because it's straight up and down and it'll hit every point 

Answer 2

The graph of a function can be a horizontal line because the x-value at each point on the line is unique, and a horizontal line passes the vertical line test. The graph of a function cannot be a vertical line because the x-value remains the same at all points, and a vertical line fails the vertical line test.