Answer:
<em>x² + y² = 841 </em>
Step-by-step explanation:
Midpoint of diameter is a center of a circle.
Coordinates of midpoint are
( ,
)
( ,
)
( ,
)
d =
Equation of a circle with center at (h, k) and radius "r" is (x - h)² + (y - k)² = r²
~~~~~~~~~~
C(20, 21)
D(- 20, 21)
( ,
) = (0, 0)
d = = √3364 = 58
r = = 29
x² + y² = 29²
<em>x² + y² = 841</em>