Answer:
(x-5)²+(y-2)²=52
Step-by-step explanation:
first find the midpoint (center of the circle)
(9+1)/2, (-4+8)/2
(5, 2) = center
then distance formula to find diameter
√(9-1)²+(-4-8)²=√64+144 = √208 = 2√52
The radius is half the diameter = √52
Formula for circle is (x-h)²+(y-k)²=r², where (h, k) is the center
Now you can plug everything in.
(x-5)²+(y-2)²=52