Question

求解题过程！大学数学

Answer 1

(a)
Let A be a mxn matrix, if AB is defined, then B is a nxk matrix,
Let the ith row of A is a row of zeros, we denote this row as a vector M1=[0,0,...,0]
then AB has a row which every element of this row is computed by M1 multiply every column of B
obviously, each result will be zero
thus, this row is a row of zeros

(b)
We can take the transpose of A, and apply the same logic above
then we take the transpose of the result, we will get AB with a column of zeros

Answer 2

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