Linear Algebra – Calculating a Basis of Vector Space U ? V

linear algebramatricesvector-spaces

So I have two vector spaces:
$ U := \langle(1,2,1,2), (1,2,3,3), (1,2,2,3)\rangle $ and
$ V := \langle(2,0,2,1), (3,2,3,2), (0,4,0,1)\rangle $

I was able to calculate the base of both $U$ and $V$:
$ B_U = \langle(1,2,1,2), (1,2,3,3), (1,2,2,3)\rangle $ since the vectors linearly independent.
$ B_V = \langle(2,0,2,1), (3,2,3,2))\rangle $ since you can write
$(0,4,0,1)$ as $2*(3,2,3,2) – 3*(2,0,2,1)$.

However, I have no clue for to do it for $U \cap V$. Could you please point out how to go about doing that and/or giving me an example?
Thanks in advance.

Best Answer

Note that there must be some overlap, since $U$ is $3$-dimensional and $V$ is $2$-dimensional. So, either $V\subseteq U$, or they intersect in a one dimensional subspace. Can you write both basis vectors of $V$ in terms of the basis for $U$? If not, then the intersection is one-dimensional. I'd just look at what vectors are in $U$ and $V$. For instance $(0,0,2,1)$ and $(0,0,1,0)$ are in $U$. Thus $(0,0,0,1)$ is also in $U$.

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