Respuesta :
[tex]\bf B= \begin{bmatrix} -1&2&5&0\\\boxed{-5}&0&9&7\\9&12&8&-1\\8&-5&0&6 \end{bmatrix}\impliedby \begin{array}{llll} b_{2,1}\\ \textit{2nd row, 1st column} \end{array}[/tex]
Answer:
-5
Step-by-step explanation:
[tex]a_{nm}\to n-\text{number of row},\ m-\text{number of column}\\\\b_{21}\to 2^{rd}\ row,\ 1^{st}\ column\\\\B=\left[\begin{array}{cccc}-1&2&5&0\\\boxed{-5}&0&9&7\\9&12&8&-1\\8&-5&0&6\end{array}\right]\begin{array}{ccc}\leftarrow\ 2^{rd}\ row\\\\\end{array}\\.\qquad\ \ \ \ \uparrow\\.\ \ \ \ \ 1^{st}\ column[/tex]