If A and B are symmetric matrices of the same order, then
(i) $A B-B A$ is a_________
(ii) $B A-2 B A$ is a________
It is given that, $A$ and $B$ are symmetric matrices of the same order.
$\therefore A^{T}=A$ and $B^{T}=B$
(i)
$(A B-B A)^{T}$
$=(A B)^{T}-(B A)^{T} \quad\left[(X+Y)^{T}=X^{T}+Y^{T}\right]$
$=B^{T} A^{T}-A^{T} B^{T} \quad\left[(X Y)^{T}=Y^{T} X^{T}\right]$
$=B A-A B$ [Using (1)]
$=-(A B-B A)$
Since $(A B-B A)^{T}=-(A B-B A)$, so the matrix $A B-B A$ is a skew-symmetric matrix.
$A B-B A$ is a _skew-symmetric matrix__
(ii)
Disclaimer: The solution has been provided for the following question.
$B A-2 A B$ is a
$=(B A)^{T}-(2 A B)^{T} \quad\left[(X+Y)^{T}=X^{T}+Y^{T}\right]$
$=(B A)^{T}-2(A B)^{T} \quad\left[(k X)^{T}=k(X)^{T}\right]$
$=A^{T} B^{T}-2 B^{T} A^{T} \quad\left[(X Y)^{T}=Y^{T} X^{T}\right]$
$=A B-2 B A$ [Using (1)]
Since $(B A-2 A B)^{T} \neq B A-2 A B$ or $(B A-2 A B)^{T} \neq-(B A-2 A B)$, so the matrix $B A-2 A B$ is neither symmetric nor skew-symmetric matrix.
$B A-2 A B$ is a neither symmetric nor skew-symmetric matrix