ANSWER
y = b
STEP-BY-STEP EXPLANATION:
The slope-intercept equation is given as
[tex]y\text{ =mx + b}[/tex]
Where m is the slope of the line
b is the intercept of the y-axis
at horizontal, slope = 0
[tex]\begin{gathered} m=\text{ 0} \\ y\text{ = 0(x) + b} \\ y\text{ = 0 + b} \\ y\text{ = b} \end{gathered}[/tex]
Hence, the equation of the line when the slope is zero is y = b
