A great teacher once told me the easiest way to tell if an equation is linear or not, by just looking at it is, if you see that the equation contains an exponent then you should automatically know that it is nonlinear. Therefore the equation y=x^2-6 is nonlinear!!!
This is because all linear functions have the highest exponent of 1. Anything equation that has a variable raised to a power other than 1 is not linear.
The equation provided as the highest exponent of 2. Thus, it's not linear.
From the provided graph, we can also see that this is quadratic instead of linear. The graph is a parabola instead of a line.
