Answer:
Correct answer: A → graphs B and D are functions
Step-by-step explanation:
A curve in the xy-plane is a function if and only if no vertical line intersects the curve more than once. The Vertical Line Test allows us to know whether or not a graph is actually a function. A function can only take on one output (y-value) for each input (x value).
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In performing the Vertical Line Test for graphs A, B, C, and D, we can easily see that graph A is not a function because the vertical lines cross the curve more than once (per each line drawn). This implies that there are 2 output values for each x value.
Graph B is a function because each vertical line draw only has one point.
Graph C is not a function because the vertical line drawn has two points in it (i.e., the input value has two output values).
Graph D is a function because each vertical lines drawn only crosses the curve once.
Therefore, the correct answer is A: Graphs B and D are functions.
