Mathematics ACT Aspire Test 2025 – 400 Free Practice Questions to Pass the Exam

A vertical line is characterized by having the same x-coordinate for every point along the line, while the y-coordinate can take on any value. Since the line in question needs to pass through the point (4, 0), this means it must have an x-coordinate of 4 for all points on that vertical line.

The equation of a vertical line is written in the form x = k, where k is the x-coordinate through which the line passes. In this instance, since the line passes through (4, 0), the equation becomes x = 4. This reflects that no matter the value of y, the x-coordinate will always be 4, thereby defining a vertical line.

The other choices describe either horizontal lines or incorrect vertical positions. For example, y = 4 describes a horizontal line that intersects the y-axis at 4, while x = 0 describes a vertical line that intersects the x-axis at 0. Similarly, y = 0 is also a horizontal line that intersects the x-axis. Thus, the only correct equation for the vertical line through (4, 0) is indeed x = 4.