Solution
= Solution
\b[True.] If $G/Z(G)$ is generated by $gZ(G)$, write $x=g^az_1$, $y=g^bz_2$ with central $z_i$; then $xy=yx$.
= Solution
\b[True.] If $G/Z(G)$ is generated by $gZ(G)$, write $x=g^az_1$, $y=g^bz_2$ with central $z_i$; then $xy=yx$.