# Algebra 1 - Lines Parallel or Perpendicular to Axes

Updated: Aug 17

This post explains and give practice opportunities related to TEKS A.2G:

write an equation of a line that is parallel or perpendicular to the X or Y axis and determine whether the slope of the line is zero or undefined;

## Instruction

Lines that are parallel to a given axis can be described by their opposite coordinate. For example, a line parallel to the x-axis can be described by its y-coordinate (e.g., y = 4). Vertical lines (parallel to y-axis) have an undefined slope and horizontal lines (parallel to x-axis) have a slope of 0.

## STAAR Practice

Between 2016 and 2022 (including redesign practice), this supporting standard has been tested 6 times on the STAAR test. Videos explaining the problems can be found below. If you'd rather take a quiz over these questions, click __here__. The videos below are linked to the questions in the quiz as answer explanations after the quiz is submitted.

To view all the posts in this Algebra 1 TEKS review series, click __here__.