Question

Let A =[1, -3, 2] and B = [-1, 3, -2]. Find A-3B.

Answer 1

[1, -3, 2] - 3[-1, 3, -2]
[1, -3, 2] - [-3, 9, -6]
[1-(-3), -3-9, 2-(-6)]
[4, -12, 8]
The three is a scalar multiplier of the matrix, B, so you simply multiply each term by 3. Because A and B have the same dimensions, you can then subtract corresponding terms.