Learn Before
Example

Verifying that Two Vertical Lines are Parallel from their Graphs

Because vertical lines have an undefined slope, the standard method of comparing slopes does not apply to them. Instead, two graphed vertical lines are verified to be parallel by confirming that they have different xx-intercepts. For instance, consider a graph showing two vertical lines: one passing through (2,0)(2, 0) and (2,1)(2, 1), and another passing through (5,0)(5, 0) and (5,1)(5, 1). The first line crosses the xx-axis exactly at (2,0)(2, 0), giving an xx-intercept of 22. The second line crosses the xx-axis exactly at (5,0)(5, 0), giving an xx-intercept of 55. Because both are vertical lines lying at distinct horizontal positions—meaning they have different xx-intercepts—they never intersect and are therefore parallel lines.

Image 0

0

1

Updated 2026-05-03

Contributors are:

Who are from:

Tags

OpenStax

Intermediate Algebra @ OpenStax

Ch.3 Graphs and Functions - Intermediate Algebra @ OpenStax

Algebra

Related