Answer: If an image of a triangle is congruent to the pre-image, then the scale factor of the dilation must be n = <u>1</u>.
Step-by-step explanation:
- A dilation is a transformation that creates an image that is the same shape as the original, but is a different size.
Since in a dilation, the corresponding the sides of the pre-image and sides of the image are proportional.
Such that ,
...........(1)
Let ΔABC is dilated to ΔA'B'C' such that AB≅A'B', BC≅B'C' and AC≅B'C'.
Then
.......(2)
From (1) and (2), 
Therefore, If an image of a triangle is congruent to the pre-image, then the scale factor of the dilation must be n = <u>1</u>.