Is the subset W x y z z 1 R3 a vector subspace of R3 Exp
Is the subset W = {(x, y, z) | z = 1} R^3 a vector subspace of R^3 ? Explain why or why not.
If W is the subset of all vectors (x, y) in R^2 such that |x| = |y|, is W a vector subspace or not?
Solution
First part
(0,0,1) is one vector in W
Multiplying it by a scalar ,2 gives the vector: (0,0,2) which is not in W
HEnce, W is not a subspace
Second Part
Consider two vectors in this subset
(3,-3)
(-4,-4)
which are both in W
Adding the two vectors gives
(-1,-7) which is not in W
Hence W is not a subspace
