Practice Test 1

A linear transformation is represented by the matrix $$A=\begin{pmatrix}3&0\0&3\end{pmatrix}.$$ Which claim about area scaling is correct for any region in the plane?

A linear transformation sends the standard basis vectors $\mathbf e_1=(1,0)$ and $\mathbf e_2=(0,1)$ to the points shown: $\mathbf e_1$ maps to $(1,0)$ and $\mathbf e_2$ maps to $(0,1)$. The matrix given is $$I=\begin{pmatrix}1&0\0&1\end{pmatrix}.$$ Which reasoning correctly interprets the matrix?