Question

What is the equation of the line that is horizontal and goes through the y-axis
at -4?

Answer 1

y = - 4

Explanation:

The equation of a horizontal line parallel to the x- axis is

y = c

where c is the value of the y- coordinates the line passes through.

The line passes through (0, - 4) with y- coordinate - 4, thus

y = - 4 ← equation of horizontal line

Answer 2

y = mx + b, m = 0. The equation becomes y = b, where b is the y-coordinate of the y-intercept.