a) $\begin{array}{l} {\left( {x + 3} \right)^2} + {\left( {y + 2} \right)^2} = 25\\ \to I\left( { - a; - b} \right) = \left( { - 3; - 2} \right),R = \sqrt {25} = 5 \end{array}$
b) $\begin{array}{l} b){x^2} + {y^2} - 6x + 2y - 6 = 0\\ \to \left\{ \begin{array}{l} 2a = 6\\ 2b = - 2\\ c = - 6 \end{array} \right. \to \left\{ \begin{array}{l} a = 3\\ b = - 1\\ c = - 6 \end{array} \right. \to R = \sqrt {{a^2} + {b^2} - c} = \sqrt {16} = 4 \end{array}$
