SOLUTION: let A = [3 -8 -5] [-4 -1 5] [-1 -9 -2] and B = [-4 -7 -1] [8 -1 8] [-3 -3 7] Find 2A - 4B.

Algebra ->  Matrices-and-determiminant -> SOLUTION: let A = [3 -8 -5] [-4 -1 5] [-1 -9 -2] and B = [-4 -7 -1] [8 -1 8] [-3 -3 7] Find 2A - 4B.      Log On


   

Question 1005797: let A =
[3 -8 -5]
[-4 -1 5]
[-1 -9 -2]
and B =
[-4 -7 -1]
[8 -1 8]
[-3 -3 7]
Find 2A - 4B.
Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
Do it for each matrix element: calculate  2%2AA%5Bi%2Cj%5D - 4%2AB%5Bi%2Cj%5D  for each pair of indexes  [i,j], i = 1 ,2 3;  j = 1, 2, 3.

Here  A%5Bi%2Cj%5D  is the element of the matrix  A  at the intersection of the  i-th horizontal row and  j-th vertical column.
Similar for  B%5Bi%2Cj%5D.

For instance,  A%5B1%2C2%5D = -8,   B%5B1%2C2%5D = -7,   and

2%2AA%5B1%2C2%5D - 4%2AB%5B1%2C2%5D = 2*(-8) - 4*(-7) = -16 + 28 = 12.