An example of a non-linear and linear function?

Non-linear: y=x^ (2) + 3x-17

Linear: y = 8x+1

Step-by-step explanation:

Quadratic, exponential, and square root functions are all non-linear. They should not be straight. There is always an x and/or y value that they will never be on. Linear functions can touch all values. That sounds very confusing, but it's better than nothing, so I'm sorry.

I don't know a better way to explain it.