Answer:
radius = 17 units
equation of the circle =( x -h)^2 +(y -k) ^2 = r^2
or , (8 -(-7))^2 + (7-(-1))^2 = r^2
or, (8+7)^2 + (7 + 1)^2 = r^2
or, (15)^2 + (8)^2 =r^2
or, 225 + 64 = r^2
or 289 =r^2
or, 17^2 = r^2
or, r = 17 units
Please check the point by inserting centre(-7,-1) in place of (h,k ) and point in (x , y) and radius in r in the following equation
(x-h)^2 + (y - k)^2 = r^ 2.