 Hello and welcome to the session. In this session we discussed the following question which says if A is an invertible matrix of order 3 and determinant of A is equal to 5 then find determinant of a joint of A. We have a property according to which we have that if A is a non-singular matrix of order n then we have determinant of a joint of A is equal to determinant of A to the power n minus 1. This is the key idea that we use for this question. Let's proceed the solution now. We are given that this A is an invertible matrix and we know that a square matrix A is invertible if and only if it is a non-singular matrix. So we say since a square matrix A is invertible A is non-singular matrix. So this means that this A is a non-singular matrix and we are given that determinant of A has value 5 that is the order of the matrix A is given to be 3. So n is equal to 3 then we have determinant of a joint of A is equal to determinant of A that is 5 to the power n minus 1 that is 3 minus 1. So this is equal to 5 to the power 2 equal to 25. So determinant of a joint of A is equal to 25. This is our final answer. This completes the session. Hope you have understood the solution of this question.