[tex]\bf \begin{array}{lllll}
&x_1&y_1\\
% (a,b)
&({{ -1}}\quad ,&{{ -5}})\quad
\end{array}
\\\\\\
% slope = m
slope = {{ m}}= \cfrac{rise}{run} \implies 0
\\\\\\
% point-slope intercept
y-{{ y_1}}={{ m}}(x-{{ x_1}})\implies y-(-5)=0(x-(-1))\\
\left. \qquad \right. \uparrow\\
\textit{point-slope form}
\\\\\\
y+5=0(x+1)\implies y+5=0\implies \boxed{y=-5}[/tex]
