Quillen plus construction (Ex)

Let $X$$<wikitex>; Let $X$ be a connected CW-complex. Let $H = [H,H] \triangleleft \pi_1X$ </wikitex> [[Category:Exercises]] [[Category:Exercises without solution]]X$ be a connected CW-complex. Let $H = [H,H] \triangleleft \pi_1X$$H = [H,H] \triangleleft \pi_1X$