Question 1139974
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The line of reflection is y = -x.  That means in the reflection of a point (p,q) the new y value is -p.<br>
The line of reflection is also x = -y (solve the given equation for x).  That means in the reflection of a point (p,q) the new x value is -q.<br>
So the image of a point (p,q) in a reflection in the y=-x is (-q,-p).<br>
A(2,1) --> A' = (-1,-2)
B(2,3) --> B' = (-3,-2)
C(3,1) --> C' = (-1,-3)