 Hello and welcome to the session. Let us understand the following problem. Evaluate the determinant 2, 4, minus 5, minus 1. Before writing the solution, let us see the key idea to the problem. Determinant of A is denoted by mod of A or determinant of A or delta. Consider a system of linear equations a1x plus b1y is equal to c1 and a2x plus b2y is equal to c2, which is associated with the square matrix A is equal to a1b1 a2b2. Thus determinant of A is equal to determinant of A is equal to a1b2 minus a2b1. Now let us write the solution. Given to us as 2 minus 5, 4 minus 1. So, using the key idea solving this we get 2 into minus 1 minus 4 multiplied by minus 5 which is equal to minus 2 plus 20 which is equal to 18. Therefore, the required answer is 18. I hope you understood the problem. Bye and have a nice day.