You can use GeoGebra to find the stationary points of a function. One method involves using CAS. Another way is to use Algebra View and Graphics View.
Recall that Solve yields exact answers (fractions and roots), while
Solve Numerically yields approximated answers given as decimal numbers.
GeoGebra Instruction 1
CAS CAS under View in Menu. f(x):=. Then press Enter. Derivative =0 after the expression and press Solve Solve Numerically f(x-value) and then press Enter. Do this for all the -values you have found. Graphics View.
If you only want to find the extrema (maxima or minima) of a function, you can just use Graphics View.
GeoGebra Instruction 2
Graphics View Algebra View and Graphics View under View in Menu. Algebra View and then press Enter. Extremum(<Function>, <Start x-Value>, <End x-Value>)
in Algebra View.
Enter the function name (, , and so on) for <Function>. For <Start> and <End>, choose a sufficient interval based on the plotted graph. For <Start>, choose an -value to the left of all the extrema of the graph, and for <End>, choose an -value to the right of all the extrema of the graph.