Question

Write the value of the determinant $\left|\begin{array}{cc}3& -1\\ 2& 1\end{array}\right|$

Answer 1

Let $A=\left|\begin{array}{cc}3& -1\\ 2& 1\end{array}\right|$

$=3\left(1\right)-\left(2\right)(-1)=3+2=5$