Standard Form of Equation of Circle

Expanded kneecaps

38. We can use the distance formula to find the radius
d=sqrt((-3-1)^2+(2-0)^2)=sqrt(16+4)=2sqrt(5)
Equation: (x-1)^2+y^2=20

40. If the circle is tangent to the y-axis, or x=0, then one of the points on the circle must have an x-coordinate of 0
The point is (0,1)
We can use the distance formula to find the radius
d=sqrt((-3-0)^2+(1-1)^2)=sqrt(9)=3
Equation: (x+3)^2+(y-1)^2=9