Consider the following combination of elementary row operations of type #1:
(i) Add row i to row j.
(ii) Subtract row j from row j.
(iii) Add row i to row j again.
Prove that the net effect is to interchange - 1 times row i with row j. Thus, we can almost produce an elementary row operation of type #2 by a combination of elementary row operations of type #1. Lest you be tempted to try, Exercise 1.9.18 proves that one cannot produce a bona fide row interchange by a combination of elementary row operations of type #1.