Answer
(b)
Work Step by Step
A matrix is in row echelon form when the following conditions are met:
1. The entry in row 1, column 1 is a 1, and only 0’s appear below it.
2. The first nonzero entry in each row after the first row is a 1, only 0’s appear below it, and the 1 appears to the right of the first nonzero entry in any row above.
3. Any rows that contain all 0’s to the left of the vertical bar appear at the bottom.
4. In reduced row echelon form,
entries above (as well as below) the leading 1 in a row are 0.
---
(a) The leading 1 in row does not have all 0's below. No.
(b) All of 1-4 are satisfied. Yes.
(c) The 28 in row 2 is leading. By rule 2, it should be a 1. No.
(d) Satisfied: 1-3, but not 4 (the 2 above the leading 1 in row 2 should be 0). No.