Lesson 2 · Matrix Algebra and Invertibility · Linear Algebra

Pretest

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

Let $A = \begin{bmatrix}2 & 1 & 0 \\ 1 & a & 1 \\ 0 & 1 & 2\end{bmatrix}$ with a in R. For which values of a is A invertible?