Reflect point (1,2)(1, 2)(1,2) across the line y=−xy = -xy=−x. The image is:
(−2,−1)(-2, -1)(−2,−1)
(2,1)(2, 1)(2,1)
(−1,−2)(-1, -2)(−1,−2)
(−2,1)(-2, 1)(−2,1)