Answer:
J'' = (0, 1)
Step-by-step explanation:
For M being the midpoint of the segment JJ', its coordinates are the average of those of J and J':
M = (J + J')/2
We can rearrange this to find J' from M and J.
2M = J + J'
J' = 2M - J
For a reflection across the line x = 1, the x-coordinate of M is 1. For a reflection across the line y = 0 (the x-axis), the y-coordinate of M is 0. Your double reflection amounts to a reflection across the point (1, 0).
The the image of J after the two reflections is ...
J' = 2(1, 0) -(2, -1) = (2·1-2, 2·0+1)
J' = (0, 1)
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In the attached image, the point after the second reflection is called J".