We have a relation R among a class of terms A, and we write R(a, b) if the relation holds between a and b. (This is of a piece with the usual definition of a relation as a class of ordered pairs. Note that R(a, b) is not the same as R(b, a), unless a=b.)

So if ~R(b,a) and (a is not b) then we cannot say ~R(a,b).

Therefore we cannot prove the conclusion using the given premises.