Question

For each relation, decide whether or not it is a function.

Answer 1

Relation 1 IS a function.

Each input is used only once, so each input is paired with exactly one output.

It doesn't matter that many of the inputs go to the same output. When you ask, "What is the output for this one input?", there is only one answer for any single input.

Relation 2 is NOT a function.

The input of "j" has two different outputs, because there are two different lines coming off of it.

Relation 3 IS a function.

Each x-value is used only once, so each input is paired with exactly one output.

Relation 4 IS a function.

Each x-value is used only once, so each input is paired with exactly one output.