Which of the following is a function?

1. Input Output Input Output Input Output

2 5 2 4 1 1

3 5 3 6 2 2

4 5 3 8 2 2

5 5 5 10 1 1

The characteristic of a function is that for each input you there is only one output.

First line: you have 2 inputs of 2, but each has different output, so is not a function.

Second line has 2 inputs of 3, but each has a different output, so is not a function.

Third line is fine.

The fourth line has 2 inputs of 5s but each one has a different output, so it also can't be a function.

Thus, the answer is the third choice: 4 5 3 8 2 2

To be a function for each input you can only have one output.

First line, you have 2 inputs of 2, but each one has a different output, so is not a function.

Second line has 2 inputs of 3, but each one has a different output, so is not a function.

The fourth line has two inputs of 5's but each one has a different output, so can't be a function.

The answer is: 4 5 3 8 2 2