Notations:
■Rmxn: the set of m x n matrices with entries in R.
■

■ det
(A): the determinant of matrix A.
■ Null
(A): the null space of matrix A.
■ rank
(A) (nullity
(A)): the rank (nullity) of matrix A.
■ In: the identity matrix of size n x n.
■

(1) True or False (If true, prove it; if false, give a counterexample or disprove it).
【題組】(i) (3%) For any
