hello :
an equation of the circle Center at the A(a,b) and ridus : r is :
(x-a)² +(y-b)² = r²
in this exercice : a =0 and b = 0 (Center at the origin)
r = OP....p(-8,3)
r² = (OP)²
r² = (-8-0)² +(3-0)² = 64+9=73
an equation of the circle that satisfies the stated conditions.
Center at the origin, passing through P(-8, 3) is : x² +y² = 73