Which equation represents a linear function?

A) : linear function.

It can be simplified to be in the form of Y = ax + b

B) : not a function at all;

all it says is that 'x' is a number;

with a little work, you can find the number.

C) : a function, but not linear;

you can see on the right side that when the parentheses are cleared,

there'll be a product of y·x there; that's enough to tell you that a graph

of y = f (x) is not a straight line.

D) : a function, but not linear;

you can see on the right side that when the parentheses are cleared,

there'll be an x² there; that's enough to tell you that a graph of y = f (x)

is not a straight line; it's probably a parabola.