Solving the euations we get the coordinates of the quadrilateral.
Slope of AB = \(\frac{1-0}{1-0}\) = 1
Slope of CD = 1
AB||CD
Slope of BD = AC = - 1
AC||BD
So they form a rectangle with all sides = 90°
The quadrilateral is cyclic as sum of opposite angles = 180° .
Now, AD = diameter of the circle equation of the circle with extremities A(0, 0)&D(6, - 4) is
(x - 0)(x - 6) + (y - 0)(y + 4) = 0
x2 + y2 – 6x + 4y = 0