00:01
Okay, so we're given two subspaces, u and v.
00:04
We want to show that u plus v, defined in this way, is also a subspace.
00:09
So we're going to show that it's non -empty, close with respect to vector addition and a scalar multiplication.
00:15
So first, non -empty.
00:17
Well, u is not empty, and v is not empty, since they're both subspaces.
00:25
So there exists u in u and v in.
00:33
In v so there exists u plus v in the set u plus v so since there's a u and a v that exist in the sets coupled to u and capital v this element u plus v is in this set so u plus v is not empty okay that's the first point now vector addition well we need to let x and y be in our set u plus v so we're going to take two elements of our set but every element of the set is of this form so we can write x is let's say u0 plus v0 and y is u0 uh u1 plus v1 where obviously u0 and u0 v1 are both in u and v0 v1 are both in v we we want to show that this sum, x plus y, is also in u plus v.
01:43
Well, x plus y is just u -not plus v0 plus u1 plus v1.
01:51
Now we can group together the u terms and the v terms...