Beginning Algebra With Applications, Chapter 5, Cumulative Exercises, Section Cumulative Exercises, Problem 12

Determine the slope of the line that contains the points whose coordinates are $(2,3)$ and $(-2,3)$.

We let $(x_1, y_1) = (2,3)$ and $(x_2, y_2) = (-2,3)$,

Using the formula for the slope of a line


$
\begin{equation}
\begin{aligned}

m =& \frac{y_2 - y_1}{x_2 - x_1}
\\
\\
m =& \frac{3-3}{-2-2}
\\
\\
m =& \frac{0}{-4}
\\
\\
m =& 0

\end{aligned}
\end{equation}
$


Then using Point Slope Formula, where $(x_1, y_1) = (2,3)$ and $m=0$


$
\begin{equation}
\begin{aligned}

y - y_1 =& m(x - x_1)
\\
y - 3 =& 0 (x-2)
\\
y-3 =& 0
\\
y =& 3

\end{aligned}
\end{equation}
$



The equation of the line is $y=3$.