We need the radius, which is distance from (4,-4) to (-4,2):
Distance = sqrt( (x2 - x1)^2 + (y2 - y1)^2 )
= sqrt( (-4 - 4)^2 + (2 - -4)^2 )
= sqrt( 64 + 36 )
= sqrt(100)
= 10
Equation of a circle centered on the point (a,b) with radius = r:
(x - a)^2 + (y - b)^2 = r^2
Equation of a circle centered on (4,-4) with radius = 10:
(x - 4)^2 + (y + 4)^2 = 100