There are two options for finding the zeros of a function in GeoGebra: The first is to use CAS, and the other is to use the Algebra View and Graphics View.
GeoGebra Instruction 1
CAS CAS under View in Menu. < <Your Expression> =0> in CAS. Solve Solve Numerically
GeoGebra Instruction 2
Algebra View and Graphics View Algebra View and Graphics View under View in Menu. Algebra View and press Enter. Root(<Polynomial>)
and press Enter.
Note! If your problem has a domain for the function, use Roots(<Function>, <Start x-value>, <End x-value>) instead. Type in the start and end values of the interval in the <Start x-value> and <End x-value> fields.