As we can see we have a horizontal line, the slope of the horizontal line is zero
the form of the equation of the line in slop-intercept form is
[tex]y=mx+b[/tex]
where m is the slope and b is the y-intercept.
In our case m=0
[tex]\begin{gathered} y=(0)x+b \\ y=b \end{gathered}[/tex]
in this case the y-intercept is b=-4
Therefore the equation is
[tex]y=-4[/tex]
ANSWER
y=-4
