In question 18, write the value of a11C21 + a12C22 + a13C23.
We have to find out the value of a11×C21+a12×C22+a13×C23
LetI=a11×C21+a12×C22+a13×C23
I= a11×-(a12a33-a13a32)+a12×(a11a33-a13a31)+a13×-(a11a32-a12a31)
I=-a11a12a33+a11a13a32+a11a12a33-a12a13a31-a11a13a32+a12a13a31
I= a11a12a33–a11a12a33+a11a13a32-a11a13a32+ a12a13a31- a12a13a31
I=0