Find the area between two concentric circles defined by
x2 + y2 -2x + 4y + 1 = 0
x2 + y2 -2x + 4y - 11 = 0  Choose the most appropriate option:
A) 11 Pi	B) 12 Pi	C) 13 Pi	D) 14 Pi	E) 15 Pi
Rewrite equations of circles in standard form. Hence equation x2 + y2 -2x + 4y + 1 = 0 may be written as   (x - 1)2 + (y + 2) 2 = 4 = 22   and equation x2 + y2 -2x + 4y - 11 = 0 as   (x - 1)2 + (y + 2) 2 = 16 = 42   Knowing the radii, the area of the ring is Pi (4)2 - Pi (2)2 = 12 Pi   correct answer is 12 Pi) 12 Pi
<result>B</result>
Find the area between two concentric circles defined by
x2 + y2 -2x + 4y + 1 = 0
x2 + y2 -2x + 4y - 11 = 0