Answer:
Center: (0,0)
Radius: 5
Step-by-step explanation:
Let O(xo,yo) be the center (of the circle) with the coordinates xo, yo.
If R is the radius, then we have:
(x-xo)²+(y-yo)²=R².
In our case: x²+y²=25, the center is at (0,0), and R²=25, so R=5
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