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- If the equation of a circle is given as $x^2+y^2=r^2$, the
__center__of the circle is located at $\cdots$?

- What is the radius of a circle whose equation is given by $x^2+y^2=9$?

- What is the radius of a circle whose equation is given by $x^2+y^2=2$?

- Find the coordinates of the center of a circle whose equation is $x^2+(y-1)^2=10$

- Find the coordinates of the center of a circle whose equation is $(x+1)^2+y^2=9$

- A circle is centered at $(2,0)$ and passes through $(5,4)$. Find its equation.

- A circle has center at $(1,-1)$ and its radius is $4$. What is its equation?

- Which of the following points is not inside the circle $x^2+y^2=100$?
- Which of the following points is on the circle $(x-1)^2+(y-2)^2=16$?
- Find the equation of a circle which passes through $(0,0),(6,0),(0,8)$.