Answer:
Center: (3,3)
Radius:
![2√(5)](https://img.qammunity.org/2022/formulas/mathematics/high-school/sn47grdgg9n1125suqje5vcr4oo9gll5fp.png)
Explanation:
Midpoint and Distance Between two Points
Given two points A(x1,y1) and B(x2,y2), the midpoint M(xm,ym) between A and B has the following coordinates:
![\displaystyle x_m=(x_1+x_2)/(2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/n87knahjq3qunkivioqektxisd8bx7zedo.png)
![\displaystyle y_m=(y_1+y_2)/(2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/98r6fuilgfwliborscobmvpxkxz5vwa982.png)
The distance between both points is given by:
![d=√((x_2-x_1)^2+(y_2-y_1)^2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/56st313bklvuad5kmg37orzosnah8k5ru7.png)
Point (5,7) is the center of circle A, and point (1,-1) is the center of the circle B. Given both points belong to circle C, the center of C must be the midpoint from A to B:
![\displaystyle x_m=(5+1)/(2)=(6)/(2)=3](https://img.qammunity.org/2022/formulas/mathematics/high-school/3b3r9f5mde1sto7mliqs7qw4wync5bs117.png)
![\displaystyle y_m=(7-1)/(2)=(6)/(2)=3](https://img.qammunity.org/2022/formulas/mathematics/high-school/dxq2q6n84d3gem9wget6xh4ivft47dk3u2.png)
Center of circle C: (3,3)
The radius of C is half the distance between A and B:
![d=√((1-5)^2+(-1-7)^2)](https://img.qammunity.org/2022/formulas/mathematics/high-school/at1ctyyyst1iqmqo0wj2e6blmo4zb54n06.png)
![d=√(16+64)=√(80)=√(16*5)=4√(5)](https://img.qammunity.org/2022/formulas/mathematics/high-school/tdrbqof6p1nnl7b7iyc5cp21rb0r3vagbt.png)
The radius of C is d/2:
![r =4√(5)/2 = 2√(5)](https://img.qammunity.org/2022/formulas/mathematics/high-school/apfr3bprxce4y7oqji3v0ezowo2h89jo5b.png)
Center: (3,3)
Radius:
![2√(5)](https://img.qammunity.org/2022/formulas/mathematics/high-school/sn47grdgg9n1125suqje5vcr4oo9gll5fp.png)