The point (–3, 5) has been reflected so that the image is at (5, –3). what is the line of reflection?

Hello,
the line is the  perpendicular bisector of A(-3,5) and B(5,-3)

Let M the middle of AB
M=((-3+5)/2,(5+(-3))/2)=(1,1)
Slope of AB= (-3-5)/(5+3)=-8/8=-1
Slope of the perpendicular : -1*?=-1=>?=1
Equation :y-1=1*(x-1)==>y=x