Show that if $1, z_1, z_2, \ldots,z_n$ are the $(n + 1)$th roots of $1$, then $$(z-z_1)(z-z_2)\cdots (z-z_n)=1+z+z^2+\ldots +z^n.$$
Make a graphic interpretation of the situation.
I already did the main result, which was to prove that identity (factor theorem, mainly what I used), but I don't understand how to give an interpretation to that, someone could explain that part to me.