Need a little help figuring whether the following subsets are actually subspaces:

1. the plane of vectors (b1, b2, b3) with b1=b2

2. the plane of vectors with b1 = 1

3. all linear combinations of v=(1,4,0) and w=(2,2,2)

4. all vectors that satisfy b1+b2+b3 = 0

5. all vectors with b1<= b2 <= b3

i'm having difficulties figuring which one satisfy the subspace requirements and how exactly the prove it... please help!!!