How do you know when a function is increasing by looking at its graph

If f′(x) > 0, then f is increasing on the interval, and if f′(x) < 0, then f is decreasing on the interval. This and other information may be used to show a reasonably accurate sketch of the graph of the function. Example 1: For f(x) = x 4 − 8 x 2 determine all intervals where f is increasing or decreasing.

The way to tell if a function is increasing via its graph is by seeing if the value of y is increasing as the value of x increases, which tends to look like the line heading towards the top right of the plane.