Question

$\left|\begin{array}{ccc}13& 16& 19\\ 14& 17& 20\\ 15& 18& 21\end{array}\right|$ is equal to:

• A. 57
• B. -39
• C. 96
• D. 0

Answer 1

Answer: (D)

Let $A=\left|\begin{array}{ccc}13& 16& 19\\ 14& 17& 20\\ 15& 18& 21\end{array}\right|$
Operate $R_2\to R_2-R_1,R_3\to R_3-R_2$
Then $A=\left|\begin{array}{ccc}13& 16& 19\\ 1& 1& 1\\ 1& 1& 1\end{array}\right|=0$
($\because$ entry of two rows are same)