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
A
and
B
are
n\times n
lower triangular matrices, then
AB
is also lower triangular. If
A
and
B
are
n\times n
symmetric matrices, then
AB
is symmetric. If
A
is a
4\times 2
matrix, then
Ax=0
has at least two free variables.
tr(ABC)=tr(BAC)
for an
n\times n
matrices
A,B
, and
C
. If
W
is a subspace of a vector space
V
and
B
is a basis for
W
, then
B
can be extended to a basis for
V
.
tr(AB)=tr(A)tr(B)
for an
n\times n
matrices
A,B
, and
C
. If
W
is a subspace of a vector space
V
and
B
is a basis for
V
, then
B
can be restricted to a basis for
W
. For any
m\times n
matrices
A
and
B
,
B=EA for some invertible ELongleftrightarrowNS(A)=NS(B).