00:01
Given the space in r2, v is a subset of r2, and v is defined as, let's say, x ,y, x greater or equal to zero, and y is greater or equal to zero.
00:25
For any u and v, which is contained in the space v, we want to show u plus v is also an element in v.
00:36
For convenience, let's define the vector u is equal to u1, u2, v is equal to v1, v2, where u1, u2, v1, v2 are all non -negative, are all greater or equal to zero.
01:03
Then by the operation, by the summation between vectors, we know the vector u plus the vector v is equal to u1 plus v1, and u2 plus v2.
01:20
By this assumption, we know this is again greater or equal to zero.
01:24
The first coordinate is again greater or equal to zero, so is the second.
01:32
That means the summation is actually an element in v.
01:39
However, we see v is not closed under multiplication...