Answer:
To determine the line of reflection if the image of Y, Y′, is at (-6, -1), we need to find the perpendicular bisector of the line segment connecting Y and Y′. This perpendicular bisector will be the line of reflection.
The midpoint of the line segment YY′ is:
[(6 + (-6))/2, (-1 + (-1))/2] = (0, -1)
The slope of the line segment YY′ is:
(-1 - (-1))/(-6 - 6) = 0/(-12) = 0
Since the slope of YY′ is 0, the perpendicular bisector of YY′ is a vertical line passing through its midpoint (0, -1), which is the y-axis. Therefore, the line of reflection is the y-axis.