Answer:
The line of reflection is
![x=1](https://img.qammunity.org/2020/formulas/mathematics/high-school/tm1gspaocfnp875ybbxdnb3weyr5fcnjyq.png)
Explanation:
In reflection, the image and the pre-image are the same distance from the line of reflection.
We choose any pair of corresponding points and find the midpoint.
The points (-1,3) and (3,3) are corresponding points.
The x-coordinate of the midpoint is
![x=(-1+3)/(2)=1](https://img.qammunity.org/2020/formulas/mathematics/college/1jrc9nd1t83w5iue8bn159h20p694694n6.png)
Hence the line of reflection is
![x=1](https://img.qammunity.org/2020/formulas/mathematics/high-school/tm1gspaocfnp875ybbxdnb3weyr5fcnjyq.png)