Question

If$\left|\begin{array}{ccc}-12& 0& \lambda \\ 0& 2& -1\\ 2& 1& 15\end{array}\right|=-360$, then the value of $\lambda$,is

• A. $-1$
• B. $-2$
• C. $-3$
• D. $4$

Answer 1

The correct option is C $-3$

$\left|\begin{array}{ccc}-12& 0& \lambda \\ 0& 2& -1\\ 2& 1& 15\end{array}\right|=-360$
Expanding along first column
$\Rightarrow (-12)\left(31\right)-4\lambda =-360$
$\Rightarrow \lambda =-3$