Given P(x,y) be equidistant from the points A(7,1) and B(3,5)
AP=BP. So, AP2=BP2
(x-7)2+(y-1)2=(x-3)2+(y-5)2
(x2-14x+)+(y2-2y+)= (x2-6x+)+(y2-10y+)
(x2+y2-14x-2y+) - (x2+y2-6x-10y+)=0
-8x+8y= -
x-y= which is the required relation.