Given A is a known 3x3 matrix, and given x is a solution of A|b (also known), then how do I find the vector b?

Question

The matrix A is:

1,5,6

0,1,1

3,8,1

And x is:

1

3

1

Answer 1

Multiply A by x (on the right) to get b: Ax=b

b = [ (1)(1) + (5)(3) + (6)(1) , (0)(1) + (1)(3) + (1)(1), (3)(1) + (8)(3) + (1)(1) ] = [22, 4, 28]

b would be written as the column vector:

22

4

28