What is the rule for finding the coordinates of an image reflected over the line y=-x

You can find the coordinates of any graph by using a coordinate table, which looks as so in the chart provided below.

What you do is you, put in the letter x and then put what y is equal to in the second box. You plug in any number for x and you solve in order to find the y coordinate. Once you do, for example for plugging in -1 into x you get 1. So your coordinate would be (-1,1).