Chapter 8 - Coordinate Geometry and Linear Systems - 8.4 - Writing Equations of Lines - Problem Set 8.4 - Page 360: 8

$y=9$

Using $y-y_1=m(x-x_1)$ or the Point-Slope Form, the equation of the line with the given point $( -3,9 )$ and slope $m= 0 $ is \begin{array}{l}\require{cancel} y-9=0(x-(-3)) \\\\ y-9=0(x+3) \\\\ y-9=0 \\\\ y=9 .\end{array}