A rotation of 270º about the origin counterclockwise (the standard) is the same as a rotation of 90º about the origin counterclockwise:
Then, when a point with coordinates P(x , y) is rotated this way, its coordinates change to
P'(y, -x).
Therefore, after this rotation, we have the following transformations:
A(0, 1) → A'(1, 0)
B(-1, 4) → B'(4, 1)
C(3, 4) → C'(4, -3)
D(2, 1) → D'(1, -2)
