Question 730924
What is the centre and radius of the circle with the equation 
x^2+y^2-2y-15=15
Standard form of equation for a circle: (x-h)^2+(y-k)^2=r^2, (h,k)=(x,y) coordinates of center, r=radius
For given equation:
x^2+y^2-2y=30
complete the square:
x^2+(y^2-2y+1)=30+1
x^2+(y-1)^2=31
center: (0,1)
radius: √31