Each of the following expressions defines a function D on the set of matrices over the field of real numbers. In which of these cases is D a 3-linear function? Justify your conclusions.
a) D(A) = A11 + A22 + A33
b) D(A) = A11 A22 A33
Recall: Let K be a commutative ring with identity, n a positive integer, and let D be a function which assigns to each matrix A over K a scalar in K. We say that D is n-linear if for each , D is a linear function of the ith row when the other (n-1) rows are held fixed.