Part I: True/False For each of the following mark as (T) true or (F) false. If you marked as false, provide a counterexample. If
Aand
Bare
n\times nlower triangular matrices, then
ABis also lower triangular. If
Aand
Bare
n\times nsymmetric matrices, then
ABis symmetric. If
Ais a
4\times 2matrix, then
Ax=0has at least two free variables.
tr(ABC)=tr(BAC)for an
n\times nmatrices
A,B, and
C. If
Wis a subspace of a vector space
Vand
Bis a basis for
W, then
Bcan be extended to a basis for
V.
tr(AB)=tr(A)tr(B)for an
n\times nmatrices
A,B, and
C. If
Wis a subspace of a vector space
Vand
Bis a basis for
V, then
Bcan be restricted to a basis for
W. For any
m\times nmatrices
Aand
B,
B=EA for some invertible ELongleftrightarrowNS(A)=NS(B). 