Matrices!!!!!!!!!!!!?

Question

The vertices of Triangle XYZ are X(1,-1) Y(2,4) Z(7,-1). The triangle is reflected over the line y=x

18. Write the coordinates of triangle XYZ in a vertex matrix

19. Graph triangle XYZ and X'Y'Z'

Answer 1

The matrix would look like this,
1 -1 1
2 4 1
7 -1 1

Obviously I can't graph it...

Answer 2

dont know how to solve it by the matriX meathord.but there is the other meathord.