Question

The reflection of a point P across a line m is the

Answer 1

Answers:  perpendicular bisector;  image

• The reflection of a point P across a line m is the point P' if line m is the   perpendicular bisector     of segment PP'
• Point P' is called the     image     of point P.

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Explanation:

If we were to reflect point P over line m to land on P', then we've gone from pre-image to image.

Let's say that Q is the point on segment PP' and it's also on line m. We consider Q the midpoint of segment PP' which means PQ and P'Q are the same length. This indicates P and P' are the same distance away from the mirror line, and that point Q bisects segment PP'. Also, line m is perpendicular to segment PP'. So that's where the "perpendicular bisector" comes from.