Answer:
x² + y² = 50
Explanation:
The circle centered at (h, k) with radius r has equation ...
... (x -h)² + (y -k)² = r²
You have (h, k) = (0, 0), so all we need to do is find r². We can do that by choosing r² so that the equation is true at the given point.
... x² + y² = (5)² + (-5)² = 25 + 25 = 50
Your equation is x² + y² = 50.