Question

Find determinant of $\left|\begin{array}{ccc}1& 0& 2\\ 2& 1& 0\\ 3& 2& 1\end{array}\right|$

Answer 1

$\left|\begin{array}{ccc}1& 0& 2\\ 2& 1& 0\\ 3& 2& 1\end{array}\right|=1(1\times 1-2\times 0)-0(2\times 1-3\times 0)+2(2\times 2-3\times 1)=1(1-0)-0(2-0)+2(4-3)=1+2=3$