What's a linear function? how do you know if it represents a linear function?

So it's B, since you have both variables of x and y. And you can get y alone, to get a constant for x, which is what makes it linear. It can't be A since the x is squared, and on a graph it's a curved shape (parabola) so it is nonlinear

Ireally don’t understand your problem do you have a better picture of it