ANSWER
The image point is [tex](1,-6)[/tex].
EXPLANATION
For a reflection in then line [tex]y=x[/tex], we simply swap the x and y coordinates.
Thus, in general the mapping for the reflection in the line [tex]y=x[/tex], is
[tex]P(x,y)\rightarrow P'(y,x)[/tex].
Hence,
[tex]P(-6,1)\rightarrow P'(1,-6)[/tex].
See graph.
