Professor Chrystal remarks (Algebra, Chap. VII. §4) that “for tntative processes no general rule can be given.” The tentative processes consist in arranging the terms in groups in such a way as either to manifest a factor common to these groups or aggregates of terms, or to bring the expression under one of the Standard Forms of which the factors are already known, such as a2-b2, a3 - b3, a3 + b3.