Question Number 74140 by MASANJAJ last updated on 19/Nov/19
Answered by Rio Michael last updated on 19/Nov/19
$${let}\:{he}\:{element}\:{be}\:{m} \\ $$$$\:\:{f}\left({m}\right)\:=\:\mathrm{2} \\ $$$$\Rightarrow\:\:\mathrm{4}{m}−\mathrm{2}=\mathrm{2} \\ $$$${m}\:=\:\mathrm{1}\: \\ $$