as a first step I say :
n>=3
r^3 - 2r^2 - r + 2 = 0
but i dont know how to continue ... can you help me?
Thank you
Hello, Narek!
Factor: .$\displaystyle r^2(r-2) - (r-2) \:=\:0$as a first step I say: .$\displaystyle r^3 - 2r^2 - r + 2 \:=\: 0$
Factor: .$\displaystyle (r-2)(r^2-1) \:=\:0$
Factor: .$\displaystyle (r-2)(r-1)(r+1) \:=\:0 \quad\Rightarrow\quad r \:=\:\text{-}1,\:1,\:2$
Got it?