Lesson 1 · Systems of Linear Equations · Linear Algebra

Pretest

Have a go before we teach it — wrong is fine, and it helps.

The augmented matrix of a system in the unknowns x1, x2, x3, x4 has been row reduced to $\begin{bmatrix}1 & 3 & 0 & -2 & 4 \\ 0 & 0 & 1 & 5 & -1 \\ 0 & 0 & 0 & 0 & 0\end{bmatrix}$. How many solutions does the system have?