Question 1040546
Question part (c) does not mean anything.  Do you want the equation of the circle instead?


(a):

Distance Formula;

{{{sqrt((-1-(-9))^2+(0-(-8))^2)}}}


(b):

Midpoint Formula;

If midpoint is the ordered pair,  (h,k), then {{{h=(-1-9)/2}}} and {{{k=(0-8)/2}}}.




(c)

Finish those computations.  The distance will give you the DIAMETER, which is twice the radius.  The midpoint in (b)  is the center, indicated as  (h,k).   If using r as the radius,  and if you want the equation for the circle, the standard form would be of a format   {{{(x-h)^2+(y-k)^2=r^2}}}.