Question

Let,
$A=\left[\begin{array}{ccc}4& 6& -1\\ 3& 0& 2\\ 1& -2& 5\end{array}\right],B=\left[\begin{array}{cc}2& 4\\ 0& 1\\ -1& 2\end{array}\right]$
$\text{and}C=\left[\begin{array}{ccc}1& 2& 3\end{array}\right]$
The expression which is not defined is:

• A. $B^{\prime }B$
• B. $CAB$
• C. $A+B^{\prime }$
• D. $A^2+A$

Answer 1

The correct option is C $A+B^{\prime }$

We can see from the options that if we take transpose of B,
$B^{\prime }$ will be of 2 x 3 matrix which cannot be added to a 3 x 3 matrix, as for the addition the order should be the same.