Prove that if AB and BA are both defined, then AB and BA are both square matrices. A
Chapter 3, Problem 3.2.28(choose chapter or problem)
Prove that if AB and BA are both defined, then AB and BA are both square matrices. A square matrix is called upper triangular if all of the entriesbelow the main diagonal are zero. Thus, the form of anupper triangular matrix is where the entries marked * are arbitrary. A more formaldefinition of such a matrix A [aij] is that aij 0 if i j.
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