

InterviewSolution
Saved Bookmarks
1. |
Give an example of twonon-zero `2xx2`matrices `A`and `B`such that `A B=O`. |
Answer» Let `A=[{:(1,1),(1,1):}]" and "B=[{:(" "1,-1),(-1," "1):}]`. Then, `AB=[{:(1,1),(1,1):}][{:(" "1,-1),(-1," "1):}]` `=[{:(1-1,-1+1),(1-1,-1+1):}]=[{:(0,0),(0,0):}]` and `BA=[{:(" "1,-1),(-1," "1):}][{:(1,1),(1,1):}]` `=[{:(" "1-1," "1-1),(-1+1,-1+1):}]=[{:(0,0),(0,0):}].` Thus, `AneO, BneO.` But, AB=BA=O. |
|