Hi I need help with this .

The lecturers at uni always say that I must test if zero is in the vector space .if its not ,then apparently its not a vector space.

But sometimes its not always possible.-when is it not possible?

THanks.

This is the actual question.

Let X={f which is a element of F such that f(x)=A+Be^x, A,B is an element of R}

Justify and determine if X is subspace of F.