Question

What is the center and radius of a circle whose equation is x2 + y2 -2x -6y -5 = 0?

Answer 1

x²+y²-2x-6y-5=0

x²-2x+y²-6y=5

x²-2x+1+y²-6y+9=5+1+9

(x-1)²+(y-3)²=15

(x-1)²+(y-3)²=(V15)²

-> centre of the circle: C(-1,-3)

-> radius of the circle: V15