What are the center and radius of a circle defined by the equation x^2+y^2- 6x+ 8y+ 21=0?
A. Center (3,-4); radius 4
B. Center (3,-4); radius 2
C. Center (-3,4); radius 2
D. Center (-3,4); radius 4
You have to complete the square. When you do this you get an equation that looks like this: (x-3)^2 + (y+4)^2 = 4. So your center is (3, -4) and your radius is 2. That looks like B to me!!!
