Algebra 1 · Functions & Sequences
Vertical Line Test
Algebra 1 · Functions & Sequences
Definition
The vertical line test says a graph is a function if no vertical line intersects it more than once.
Examples
- A straight line passes the test.
- A circle fails the test.
Key rule
If any vertical line hits the graph twice, it is not a function.
Memory hook
One hit per vertical line = it is a function.