Question 387192
The idea is that if {{{n^2}}} is even, then {{{n}}} is even (you can prove this by contraposition). So {{{n=2k}}} for some integer k.



So {{{n^2=(2k)^2=4k^2}}}. So because {{{n^2=4k^2}}}, this means that {{{n^2}}} is a multiple of 4.