Question

find the equation of the line below (3,-1)

Answer 1

use:
\[(y-y_0)=m(x-x_0)\]
but I think you're missing another point. Find the slope (m) by using: \[m=\frac{ y_2 - y_1 }{ x_2 - x_1 }\]

Answer 2

do mean below x-axis...??