The Horizontal Line Test
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
The horizontal line test reads a graph for one-to-one: if any horizontal line crosses more than once, some output belongs to two inputs.
Show
On y = x², the horizontal line y = 4 hits (2, 4) and (−2, 4) — a function, but not one-to-one.
Builds on
- Nothing — this is a starting point.
Unlocks
- Nothing yet depends on this.