Question

O determinante de A, det A, sendo A = [3 -1, 7 -4], é:
a. 5
b. -19
c. 18
d. -5​

Answer 1

$\text{Sabemos\ que} \\ \\ \begin{vmatrix}a & b\\c & d\end{vmatrix} =ad-bc\ \\ \\ \text{Logo,} \\ \\ \begin{vmatrix}3 & -1\\7 & -4\end{vmatrix} =-12-( -7) =-5$