Chapter 1, Equations and Graphs - Section 1.3 - Lines - 1.3 Exercises - Page 113: 37

$x=2$

RECALL: A vertical line has an undefined slope and has an equation of the form $x=h$ where $h$ the x-coordinate of all the points on the line. The line has an undefined slope therefore the line must be vertical. The vertical line passes through the point $(2, -1)$. The x-coordinate of the point $(2, -1)$ is $2$. Thus, the equation of the line is $x=2$.