Question

A point that is 7 units from the y-axis is reflected across the y-axis. What is the distance of this new point from the y-axis? Explain how you know.

Answer 1

7 units

Explanation:

When you reflect a point (x, y) across the y-axis, the y-coordinate remains the same, but the x-coordinate gets the opposite sign: it becomes (-x, y).

Thus, if a point A, say, (-7, 5) is seven units to the left of the y-axis, its reflection A' will be the same distance to the right, at (7,5).

In the image below, Point A is seven units to the left of the y-axis. Its reflection, Point A', is seven units to the right of the axis.