Question

$\left|\begin{array}{ccc}24& 25& 26\\ 25& 26& 27\\ 26& 27& 27\end{array}\right|$ is equal to

• A. 0
• B. -1
• C. 1
• D. 2

Answer 1

Answer: (C)

Let $\Delta \left|\begin{array}{ccc}24& 25& 26\\ 25& 26& 27\\ 26& 27& 27\end{array}\right|$
Applying $R_2\to R_2-R_1$
and $R_3\to R_3-R_2$
$\Delta =\left|\begin{array}{ccc}24& 25& 26\\ 1& 1& 1\\ 1& 1& 0\end{array}\right|$
$=1[25-26]-1[24-26]$
$=-1+2=1$