Proving Vector Space of U is Null Space of T

[franky2727]

got a question show that the null space of T is a vector space of U given the mapping T:U->V

i know that null space or kernal of T is kerT={uEU: T(u)=0} and is a subset of U but don't have a clue where to start applying this to my question?

 

[radou]

Well, how do you show that a subset of U is a subspace of U?