Quillen plus construction (Ex)

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

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$H = [H,H] \trianglleft \pi_1X$