Question

which of these relations is a function?

Explanation:

Step1: Recall vertical line test

A relation is a function if any vertical line drawn intersects the graph at most once.

Step2: Test top-left graph

A vertical line intersects this vertical line graph infinitely many times. It fails the test.

Step3: Test top-right graph

A vertical line intersects this circle graph twice. It fails the test.

Step4: Test bottom-left graph

Any vertical line intersects this parabola at most once. It passes the test.

Step5: Test bottom-right graph

Any vertical line intersects this V-shaped graph at most once. It passes the test.

Answer:

The bottom-left downward-opening parabola and the bottom-right V-shaped graph are functions.