Then subtraction is the inverse operation of addition, defined entrywise by: A + ( − − 1 ) B = ( A 0 , A 1 , A 2 , A 3 ) + ( − − 1 ) ( B 0 , B 1 , B 2 , B 3 ) = ( A 0 − − B 0 , A 1 − − B 1 , A 2 − − B 2 , A 3 − − B 3 )