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# The radius of the circle given by $x^2+y^2+z^2+2x-2y-4z-19=0=x+2y+2z+7,$ is

$\begin {array} {1 1} (a)\;4 & \quad (b)\;3 \\ (c)\;2 & \quad (d)\;1 \end {array}$
Can you answer this question?

(b) 3
answered Nov 7, 2013 by