In this exercise we have to use the function definition to describe what is means, so we can say that:
Is a expression that involving one or more variables.
What is a function ?
An expression or rule that defines a relationship between two variables can be one independent and other dependent variable. Some examples of function is:
[tex]BX+C\\Y^2=X\\4X+7Y=0[/tex]
See more about functions at brainly.com/question/5245372