Question

The vertices of ΔABC are A(−2,4), B(−2,5), and C(−5,2). If ΔABC is reflected across the line y=1 to produce the image ΔA'B'C', and the coordinates of the vertex B'.The coordinates of B' after a reflection across the line y=1 are

Answer 1

A reflection across the y = 1 consists:

T(x,y) => T'( x, 1 - (y - 1) )

then, for the given points, you obtain:

(-2,5) => (-2 , 1 - (5 - 1)) = (-2 , 1 - 4) = (-2 ,-3)

(-2,4) => (-2, 1 - (4 - 1)) = (-2 , 1 -3) = (-2 ,-2)

(-5,2) => (-5 , 1 - (2 -1)) = (-5, 1 - 1) = (-5 , 0)

Hence, the coordinates of point B' are (-2,-3)