The graph of the equation 4x^2 - 12x + 4y^2 + 16y + 17 = -4x + 2y + 5 is a circle. Find the radius of the circle.
Rearrange as
4x^2 - 8x + 4y^2 + 14y = -12 divide through by 4
x^2 - 2x + y^2 + (7/2)y = -3 complete the square on x, y
x^2 - 2x + 1 + y^2 + (7/2)y + 49 /16 = -3 + 1 + 49/16
(x - 1)^2 + (y + 7/4)^2 = 17 / 16
The radius = sqrt ( 17/16) = sqrt (17) / 4
+1911 
