I think matrix A is created by the given vectors (1,0,1) and (0,1,-2) in this case.
The material is from Orthogonal Bases. Please explain each step of your solution.
Construct the matrix proj(v)....© BrainMass Inc. brainmass.com March 4, 2021, 8:31 pm ad1c9bdddf
This shows how to construct a given matrix using an orthogonal basis.