Which of these equations represent functions where x is the input and y is the output? Select each correct answer.

A - x=5

B - y=4

C - y=3x

D - x=3y

E - x+y=5

The first equation is a constant. There is no input necessary, and the output remains 5.

The second equation is also a constant. The output is 4.

In the third equation, y depends on what value of x you use. x is the input and y is the output.

In the fourth equation, x depends on what value of y you use. The way it is written, y is the input and x is the output.

In the last equation, either x or y could be the input. The other variable would change depending on which variable you replace with a number.