To find the scale factor used in the dilation of line segment AB, we need to compare the lengths of AB and A' B'.
Length of AB:
Using the distance formula, we can calculate the distance between points A and B:
AB = √((-3 - (-1))^2 + (-5 - (-3))^2) = √((-2)^2 + (-2)^2) = √8
Length of A' B':
Similarly, we can calculate the distance between points A' and B':
A' B' = √((-9 - (-3))^2 + (-15 - (-9))^2) = √((-6)^2 + (-6)^2) = √72
The scale factor can be obtained by dividing the length of A' B' by the length of AB:
Scale factor = A' B' / AB = √72 / √8 = √(72/8) = √9 = 3
Therefore, the scale factor used in the dilation of line segment AB is 3.