Question

find the coordinates of the vertices of the triangle after a reflection across the line y= 3 and then across the line x = -1​

Answer 1

Answer: A

Explanation:

Reflection across y = 3

The simplest way to calculate the new coordinates is to draw y = 3, count how many units away the point is from y = 3, then count the same number of units from y = 3 in the OPPOSITE direction to find the reflection. (see attachment - blue color)

U = (-5, 4) is 1 unit above y = 3

U' = (-5, 2) is 1 unit below y = 3

T = (0, 5) is is 2 units above y = 3

T' = (0, 1) is 2 units below y = 3

S = (-4, 2) is 1 unit below y = 3

S' = (-4, 4) is 1 unit above y = 3

Reflection across x = -1

The simplest way to calculate the new coordinates is to draw x = -1, count how many units away the point is from x = -1, then count the same number of units from x = -1 in the OPPOSITE direction to find the reflection. (see attachment - red color)

U' = (-5, 2) is 4 units to the left of x = -1

U'' = (3, 2) is 4 units to the right of x = -1

T' = (0, 1) is 1 unit to the right of x = -1

T'' = (-2, 1) is 1 unit to the left of x = -1

S' = (-4, 4) is 3 units to the left of x = -1

S'' = (2, 4) is 3 units to the right of x = -1