(Only doing first six because there's just too many)
Reflection over the x-axis: (x, -y)
Reflection over the y-axis: (-x, y)
Reflection over both axes: (-x,-y)
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e.g. (-5,-9) over x-axis -> (-5,9), 4th letter
(2,-3) over y-axis -> (-2,-3), 9th letter
(6,4) over both axes -> (-6,-4), 17th letter
(-7,2) over both axes -> (7,-2), 12th letter
(-3.9,5) over y-axis -> (3.9,5), 1st letter
(4, 1 1/2) over x-axis -> (4, -1 1/2), 19th letter