Algebra and Trigonometry 10th Edition

Av = $\begin{bmatrix} -4\\ 2\\ \end{bmatrix}$ The transformation is a reflection across the y-axis.
First rewrite the vector as a matrix: v = $\begin{bmatrix} 4\\ 2\\ \end{bmatrix}$ Then multiply the two matrices to find Av: Av = $\begin{bmatrix} (-1)(4) + 0(2)\\ 0(4) + 1(2)\\ \end{bmatrix}$ = $\begin{bmatrix} -4\\ 2\\ \end{bmatrix}$ The transformation is a reflection across the y-axis.