Which of the following transformations does not preserve congruence?
(pick an answer)
(x,y)
(-y,-x)
(x,y)
(9x,9y)
(x,y)
(x+9,y+9)
(x,y)
(-x,-y)
(x,y)
(9x,9y)
(pick an answer)
(x,y)
(-y,-x)
(x,y)
(9x,9y)
(x,y)
(x+9,y+9)
(x,y)
(-x,-y)
(9x,9y)