Answer:
4 units
Step-by-step explanation:
Distance formula:
[tex] \sqrt{(x1 - x2)^{2} + (y1 - y2)^{2} } [/tex]
[tex]length \: of \: line \: xy \\ = \sqrt{(3 - 3 )^{2} + (1 - ( - 3))^{2} } \\ = \sqrt{(1 + 3)^{2} } \\ \ = \sqrt{4^{2} } \\ = 4 \: units[/tex]
Or since both coordinates lie at x=3, the line is a vertical line so you can simply count the increase in y to find the distance of the line.
1-(-3)= 4 units
