Rewrite system of RRR ≡ NULL, FF ≡ NULL, RRF ≡ FR. Show that each string in {F,R}* is equiv. to one of the six strings: NULL, R, RR, F, FR, FRR. A hint is to use induction and ask if every string of length <=2 equiv. to one of the six strings. If a string w has length n ≥ 2, then either w = Rx with length of x = n − 1, or w = F x with length of x = n − 1.)
Am I understanding it correctly by saying the R string from the six is not equiv. because it doesn't match the rewrite system given?