Find the transformation matrix that reflects a point (x,y)(x, y)(x,y) across the line y=−xy = -xy=−x.
(−100−1)\begin{pmatrix} -1 & 0 \\ 0 & -1 \end{pmatrix}(−100−1)
(0110)\begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix}(0110)
(0−1−10)\begin{pmatrix} 0 & -1 \\ -1 & 0 \end{pmatrix}(0−1−10)
(100−1)\begin{pmatrix} 1 & 0 \\ 0 & -1 \end{pmatrix}(100−1)