Question 698712
A horizontal line will always have the equation y = a for some number a. You can think of a horizontal line as the set of all points that share a y-value. The point (0,5) has a y-value of 5, so the horizontal line is the set of all points with a y-value of 5, which has the equation y = 5.<br>

A vertical line will always have the equation x = a for some number a. In a similar sense to the horizontal line, you can think of a vertical line as the set of all points with the same x-value. With the point (0,5), the x-value is 0, so the vertical line is the set of all points with an x-value of 0 which is the line x = 0.