Chapter 7: Q66E (page 325)
(a) Give an example of a 3 脳 3 matrix A with as many nonzero entries as possible such that both span() and span(,) are A-invariant subspaces of . See Exercise 65.
(b) Consider the linear space Vof all 3 脳 3 matrices A such that both span () and span (,) are A-invariant subspaces of . Describe the space V (the matrices in V 鈥渉ave a name鈥), and determine the dimension of V.
Short Answer
The solutions are,
(a)
(b) those are upper triangular matrices, and dim V = 6