Find the equation of a circle concentric with the circle x2 + y2 – 6x + 12y + 15 = 0 and has double of its area.
Given equation of the circle is :
x2+y2-6x+12y+15=0
(x-3)2+(y+6)2=(30)
Hence, centre is (3, -6) and radius is
Since, the required circle is concentric with above circle, centre of the required circle is (3, -6).
Let its radius be r
Area of circle=
r2=60
Equation of required circle (x-3)2+(y+6)2=60
x2+y2-6x+12y-15=0