\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
Find the single matrix representing a reflection in the y-axis followed by a horizontal stretch of scale factor 3.
$$ \mathbf{T} = \begin{pmatrix}\input{145141}{}{3em}{2em}{}{} & \input{245141}{}{3em}{2em}{}{}\\ \input{345141}{}{3em}{2em}{}{} & \input{445141}{}{3em}{2em}{}{}\\ \end{pmatrix}$$