ANSWER
B'(5,-2).
EXPLANATION
The coordinates of B are (-2,5).
We want to find the image of this point after a reflection in the line y=x.
The mapping is
[tex](x,y)\to (y,x)[/tex]
We just have to swap the ordered pairs.
[tex]( - 2,5)\to (5, - 2)[/tex]
Hence the image of B(-2,5) is B'(5,-2).
The correct answer is (5,-2).
