For a 270-degree counterclockwise rotation of the point \((x, y)\) in the coordinate plane, the correct mapping is:
\[ (x,y) \rightarrow (y, -x) \]
This transformation reflects the new position of the point after a 270-degree rotation around the origin.
To summarize:
- A 90-degree counterclockwise rotation maps \((x, y)\) to \((-y, x)\).
- A 180-degree rotation maps \((x, y)\) to \((-x, -y)\).
- A 270-degree counterclockwise rotation (or 90 degrees clockwise) maps \((x, y)\) to \((y, -x)\).
Thus, the answer is:
\[ (x,y) \rightarrow (y, -x) \]