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The standard method is to use a pencil, a graph paper and a straightedge.
Using the function definition, find the coordinates of any two points on the line.
For example, take x = 0 and determine f(x) = f(0) = 0, according to the function.
Next take x = 1 and determine f(x) = f(1) = -1, according to the function.
So, the two points are (0,0) and (1,-1).
Plot these points in a graph paper.
Next take the straightedge and draw a straight line through the two points.
It is how it was touched in schools for hundreds years.
There is another, more modern way (we live in XXI century).
Go to website www.desmos.com/calulator.
Find there free of charge plotting tool for common use.
Print the equation of the function in the port window.
Get your plot in the next second.
