The line passing through points [tex](x_1, y_1)[/tex] and [tex](x_2, y_2)[/tex] is given by
[tex]\dfrac{x-x_1}{x_2-x_1}=\dfrac{y-y_1}{y_2-y_1}[/tex]
Plug your values to get
[tex]\dfrac{x-3}{4-3}=\dfrac{y+1}{7+1} \iff \dfrac{x-3}{1}=\dfrac{y+1}{8}[/tex]
Multiply both sides by 8 to get
[tex]8(x-3)=y+1 \iff y=8x-24-1=8x-25[/tex]
