Consider a vector space V over a field F. Let K be a subfield of F.
Prove that V over K is a vector space if we retain the same addition operation and restrict scalar multiplication to scalars from K
Work so far
I figure if we just prove that there exists the 0 element, and that addition and scalar multiplication are closed, the statement.
I know there exists a zero element, as 0x=0 for
and
, and this 0 is also in K
Under scalar multiplication, all scalars from K are also in F, so if it was closed under F it will also be closed under K
But how do I resolve addition if the same operation is retained.