Suppose G$G$ is solvable,and π(G)= and {2,m,n}$\pi(G)= \{2,m,n\}$, O_{2}(G)=1$O_{2}(G)=1$.Then Then can we use the solvability of G proof$G$ to prove that O_{2^{\prime}}(G) \neq 1$O_{2^{\prime}}(G) \neq 1$?Let \bar{G}= G Let / O_{2^{\prime}}(G)$\bar{G}= G / O_{2^{\prime}}(G)$,what what about O_{2}(\bar{G})$O_{2}(\bar{G})$? I think O_{2}(\bar{G})=\bar{R} $O_{2}(\bar{G})=\bar{R}$,R $R$ is the Sylow 2-subgroup of G$G$.Is Is this right?What What is the specific proof?