Comments on Important Facts
One should emphasize that vectors are always included as special cases of matrices and
that those two operations have properties [formulas (3), (4)] similar to those of operations
for numbers, which is a great practical advantage.
SOLUTIONS TO PROBLEM SET 7.1, page 277
, undefined, undefined
Similar (and more important) instances are the scaling of equations in linear
systems, the formation of linear combinations, and the like, as will be shown later.
4 and 0, 2, 0. The concept of a main diagonal is restricted to square matrices.
No, no, no. Transposition, which relates row and column vectors, will be discussed
in the next section.
The incidence matrices are as follows, with nodes corresponding to rows and
branches to columns, as in Fig. 152.