Is the minor chosen correctly?

Question

Linear algebra

I wanted to ask if the minor from the photo was chosen correctly?
in general, there is a little strange minor in the book, in most of the Internet resource it is said about the minor Mij aij of the element, which is obtained by taking the determinant from the original matrix and deleting i row and j column. what is the difference between these 2 minors?

Answer 1

Yes, it's a minor.
There is no particular difference between the minor of an element and the minor taken by rows and columns, it's just the same definition only through the deletion of the element. After all, you still get what you can choose from rows and columns.