Mathematics for IGCSE & O level - Transformations (Section 2 - No. 46)
If a point is reflected across the y-axis, how do the coordinates change?
(x, y) becomes (-x, y)
(x, y) becomes (x, -y)
(x, y) becomes (-x, -y)
(x, y) stays the same
Paliwanag
Reflection over y-axis negates the x-coordinate.