If 3x + 2y = 3 and 2x + 5y = 1 are conjugate lines w.r.t the circle $x^2+y^2=r^2$ then $r^2$ =

$$\begin{gathered} \mathrm{Apply} \mathrm{the} \mathrm{condition} \\ {\mathrm{r}}^2({\mathrm{l}}_1{\mathrm{l}}_2+{\mathrm{m}}_1{\mathrm{m}}_2)={\mathrm{n}}_1{\mathrm{n}}_{2 } \\ \mathrm{where} {\mathrm{l}}_1=3,{\mathrm{m}}_1=2,{\mathrm{n}}_1=-3 \mathrm{and} {\mathrm{l}}_2=2,{\mathrm{m}}_2=5,{\mathrm{n}}_2=-1 \\ \Rightarrow {\mathrm{r}}^2(6+10)=3 \\ \Rightarrow {\mathrm{r}}^2=\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$16$}\right. \end{gathered}$$