Given the following matrix A, find an invertible matrix U so that UA is equal to the reduced row-echelon form of A:

Question

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A =
3 3 9 −6
3 3 9 −6
−2 −1 −8 1
I believe the answer for U is
3 0 0
0 -1 -2
0 0 -1

Answer 1

well what is U * A using your U
3 +0 +0
0 -1 -2
0 +0 -1
times
A = (interesting, first two equations (rows) the same :()
3 3 9 −6
3 3 9 −6
−2 −1 −8 1
==========================
well for the first two rows I get
9 +9 27 -18
1 -1 +7 + 4

reduced row echelon ?????
to check use
https://www.emathhelp.net/calculators/linear-algebra/reduced-row-echelon-form-rref-caclulator/?i=%5B%5B3%2C3%2C9%2C-6%5D%2C%5B3%2C3%2C9%2C-6%5D%2C%5B-2%2C-1%2C-8%2C1%5D%5D&steps=on