Answer
1. Graphing
2. Table
Work Step by Step
First we can see if a function is linear by graphing it. If the graph is a straight line then we can conclude that the function is linear because that is the definition of a graph of a linear function.
Another way we can deduce that a function is linear is by seeing a table of points of the function. If we can see that the difference between the y-coordinates is constant, then we can deduce that the function is linear.