Question

dadas as matrizes A= |0 3| , B= |-2 4| , C- A.B
                                |2 -5|        |0 -1|

determine C21:

Answer 1

|0 3|    B= |-2 4|
|2 -5|        |0 -1|

A . B =
(0 * -2, + 3 * 0) = c11 = 0
(0 * 4 + 3 * 1) = c12 = 3
(2 * -2 + -5 * 0) = c21  = -4 + 0 = -4
(2 * 4 + -5 * -1) = c22  = 8 + -5 = 3

C = 
I0   3I
I-4   3I

C- A.B = 

I0   3I           menos         I0   3I
I-4  3I                              I-4  3I


0 - 0 = a11 = 0
3 - 3 = a12 = 0
-4 - -4 = a21 = 0
3 - 3 = a22 = 0

C - A . B = 
I0    0I
I0    0I

Matriz nula   

O c21 será -4