\(\bf \begin{array}{lllll}
&\underline{x_1}&\underline{y_1}&x_2&y_2\\
% (a,b)
&({{ 2}}\quad ,&{{ -1}})\quad
% (c,d)
&({{ 6}}\quad ,&{{ 1}})
\end{array}
\\\quad \\\\
% slope = m
slope = {{ \boxed{m}}}= \cfrac{rise}{run} \implies
\cfrac{{{ y_2}}-{{ y_1}}}{{{ x_2}}-{{ x_1}}}
\\ \quad \\\\
% point-slope intercept
y-{{\underline{ y_1}}}={{\boxed{ m}}}(x-{{ \underline{x_1}}})\qquad \textit{plug in the values and solve for "y"}\\
\qquad \uparrow\\
\textit{point-slope form}\)