In: Advanced Math
Suppose the system AX = B is consistent and A is a 6x3 matrix. Suppose the maximum number of linearly independent rows in A is 3. Discuss: Is the solution of the system unique?
Since the system is consistent,
there is at least one solution, say
. Let
be any solution to
, and let
;
then
Thus, .
Since the maximum number of linearly independent rows in
is
, we
know that
is the row-rank of
. Since
row-rank and column-rank of a matrix are identical, we conclude
that column-rank of
is also
. Thus, all the
columns of
are linearly
independent. Since the vector
is a linear
combination of the columns of
, namely,
, where
and
are
columns of
, we conclude that
implies
. This
implies
Thus, if are
solutions to
then
; hence, the
system
has a unique
solution.