## Linear Algebra and Its Applications (5th Edition)

$$\begin{bmatrix} 1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 2 \\ \end{bmatrix}$$
The above system is undetermined because it has fewer equations (2) than unknowns (3). It is inconsistent because row reduction yields a row with coefficients of $0$ somehow adding up to $1$, which is impossible.