Answer
$2y+9=0$
Work Step by Step
Using $y-y_1=m(x-x_1)$ or the point-slope form of linear equations, the equation of the line passing through $
\left(
-\dfrac{5}{8},-\dfrac{9}{2}
\right)$ and with a slope of $m=
0
$ is
\begin{array}{l}\require{cancel}
y-\left( -\dfrac{9}{2} \right)=0 \left(x-\left( -\dfrac{5}{8} \right) \right)
\\\\
y+\dfrac{9}{2}=0 \left(x+\dfrac{5}{8} \right)
\\\\
y+\dfrac{9}{2}=0
\\\\
2y+9=0
.\end{array}