Answer to Question #6319 in Algebra for Brandy

Question

(each [] is a new row in the matrix)
Find -7A-4B for
a=[7, -4, -7][-1, -2, 6][2, 9, -9] and b=[7, -4, -7][-1, -2, 6][2, 9, -9]

Answer 1

-7*[7, -4, -7][-1, -2, 6][2, 9, -9] - 4*[7, -4, -7][-1, -2, 6][2, 9, -9] = [-49, 28, 49][7, 14, -42][-14, -63, 63] - [28, -16, -28][-4, -8, 24][8, 36, -36]
= [-77, 44, 77][11, 22, -66][-22, -99, 99]