Given:
The vertices of a triangle are A (-2, 4) , B (-2,3) , and C (-5,2).
Triangle ABC is reflected across the line y = -1 to produce the image of A'B'C'.
To find:
The coordinate of B' after a reflection across the line y=-1.
Solution:
If a figure is reflected across the line y=b, then



The given triangle ABC is reflected across the line y=-1. So, the rule of reflection is


The coordinates of point B are (-2,3). So,


Therefore, the coordinates of point B' are (-2,-5).