## 8th Ed, §1.5, Exercise 12

then at least one entry in the third row must be a zero — but

Show that if A=

1 0 0 0 1 0 abcis an elementarymatrix,notc.

[Hints: CanAbe elementary ifc= 0?

If 0 ≠c≠ 1, what more can be said aboutaandb?

And what, finally, if insteadc= 1?]

First posted: 05 Feb 2006.