Question

Quadrilateral PQRS is located in the first quadrant of a coordinate plane. One of its vertices, P, is located at (1, 7). If the quadrilateral is reflected across the y-axis, what is the location of point P'?

(1, -7)
(-1, 7)
(7, -1)
(-7, 1)

Answer 1

Reflecting across the y-axis negates the x-coordinate: (x, y) → (−x, y).
So P(1, 7) maps to P'(−1, 7).