If we subtract the rows that are equal,
the result will be a row all zeros.

In a row-reduced matrix ( see P3 property), these go to the bottom, so we can safely say that the last row has all zeros. (there may or may not be other all-zero rows)

In a row-reduced matrix ( see P3 property), these go to the bottom, so we can safely say that the last row has all zeros. (there may or may not be other all-zero rows)