Mathematical Methods · functions and relations · manipulative

Vertical line test

Drag the vertical probe. A relation is a function only if every vertical line meets the graph in at most one point.

relation vertical probe intersections

Drag the vertical line · scroll zoom · pan · Shift+drag an axis to dilate

This vertical line

Intersection count
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Probe

Show vertical probe
turn off to inspect the graph alone, then drag to test
-3.5

Working