No.
A linear relationship. Added: And a function.
It is a quadratic function which represents a parabola.
No. A proportional relationship between "y" and "x" must be of the form:y = kx where "k" can be any constant. Thus, y = 16x would work perfectly. However, the additional "+4" makes it impossible to convert it to this form.
Only if it's a function.
Yes.
yes
No, that is a equation.
No.
Yes.
Yes.
No. It is an equation. A function would link the variable x to another variable - possibly denoted by y. It is a relationship between two (or more) variables.
Yes.