Question

which graph represents a function?

Explanation:

Step1: Recall vertical - line test

A graph represents a function if and only if any vertical line drawn on the coordinate - plane intersects the graph at most once.

Step2: Analyze first graph

The first graph (a parabola opening to the right) fails the vertical - line test. A vertical line can intersect it at two points.

Step3: Analyze second graph

The second graph (a "V" - shaped graph opening to the left and right) fails the vertical - line test. A vertical line can intersect it at two points.

Step4: Analyze third graph

The third graph (two vertical lines) fails the vertical - line test. There are multiple y - values for a single x - value.

Step5: Analyze fourth graph

The fourth graph (two horizontal lines) passes the vertical - line test. Any vertical line will intersect it at most once.

Answer:

The fourth graph (the one with two horizontal lines) represents a function.