My misunderstanding, its not that i want to do a 2 page solution to this question, its purely out of necessity in answering an assignment question unfortunately. How confident are you that the answer is in fact -728? Just to be sure, i hope the characters alpha (4th row, 5th column) and beta (6th row, 3rd column) amongst the other intergers within the array, have been taken into account, and not misinterpreted in any manner.
it's a lot of boring work!! but yes, it's the answer.
let me introduce you another example so you can follow the process and apply it in your problem: let be matrix such that now let's compute
does this make sense? the thing is: make zeros and then apply cofactors according to the row or column you created zeros.