I recently have started studyng about free algebras and I want to know what kind of methods or approaches are there to prove that free algebra $A$ is nilpotent with nilpotency index $n.$
Let me remind that algebra $A$ is called nilpotent with niplotency index $n$, if for some small $n$ we have $A^n=0.$
My question is that if there is a free algebra $A$ that satisfied an identity $f = 0$ what kind of approaches are there to prove algebra $A$ is nilpotent(if it is nilpotent). I know only one method: if $A$ is nilpotent with nilpotency index $n$, then we can calculate all the elements in degree $n$ obtained from $f$. If these elements are $0$ then $A$ is niplotent.