Question

The point (2, –4) is reflected across the line y = –1. What are the coordinates of the image?

Answer 1

How far is y = -4 from y = -1

Answer 2

Since you are reflecting around a y value, your x value will not change. The reflected y-value must be the same distance from the axis of symmetry. so the distance from y = -4 to
y = -1 is 3 units. This is how much you must raise y = -1 by to reflect it. y = -1 + 3 = 2
So your new coordinates are (2, 2) Another way to think about it: what point along with (2,-4) gives a midpoint of (2, -1)?