Answer: (1,5) (...midpoint..., ...negative reciprocal...)
Step-by-step explanation:
What is the line of reflection? It is the line across which the point is reflected. By definition of reflection, the distance of the preimage and the image from this line are the same. Since the distances are the same, they meet exactly halfway from each other. This means if you find the midpoint of the preimage and image you find a point on the line of reflection. But one point is not enough. Slope or another point is necessary. Slope is a lot easier to get.
Think about it. The line of reflection will always be perpendicular to the line connecting the preimage and image. Therefore its [line of reflection] slope will be the negative reciprocal of the slope of the preimage and image. Now you have slope and a point and thus a defined line of reflection
Hope this is helpful :)