Find the area between two concentric circles defined by
x2 + y2 -2x + 4y + 1 = 0
x2 + y2 -2x + 4y - 11 = 0	Choose one
A) 40 Pi B) 19 Pi C) 12 Pi D) 46 Pi E) 22 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 12 Pi
<result>C</result>
Find the area between two concentric circles defined by
x2 + y2 -2x + 4y + 1 = 0
x2 + y2 -2x + 4y - 11 = 0