I'd like to know how I can prove "the set of all vectors∈
with
and
" that it is vector space or not?


By using the definition of vector space. But since you are already given that this is a set of vectors, you know that things like "associative law", etc. are true. What you need to do is see if, given that, [tex]v_3- v_4= 1[/itex],
, and
then the same is true of the sum
. That is, is
and
. I recommend you look closely at that last equation!