Ahorizontal line passes through the point (5, -1). which point is also on this line?
(0,0)
(-1,5)
(5, 4)
(-2,-1)

Step-by-step answer with explanations:

Recall that a coordinate pair such as (5,-1) has two components.

The first (5, -1) means that the point is situated at x=5.

The second (5, -1) means that the point is situated at y=-1.

Now, a horizontal line through (5,-1) means that ALL points on the line have y-coordinate equal to -1, so that any point with y=-1 will lie on this horizontal line.  An example would be (-2,-1).

A vertical line through (5, -1) means that ALL points on the line have x-coordinate equal to 5, so that any point with x=5 will lie on this vertical line.  An example would be (5,4).

irrational, cannot