# d

• October 13th 2008, 11:17 AM
I Congruent
Subspaces
OOPS I MESSED UP THE TITLE CAN ANY1 TELL ME HOW I CAN CHANGE IT?

Let $V = R^3$, and consider the following subsets of V.

$U_1 = \{ t \begin{pmatrix}
1\\
0\\
0\end{pmatrix} : t \in R \}$

$U_2 = \{ t \begin{pmatrix}
0\\
1\\
0\end{pmatrix} : t \in R \}$

$U_3 = \{t \begin{pmatrix}
1\\
1\\
1\end{pmatrix} : t \in R \}$

$U_4 = \{ \begin{pmatrix}
r\\
s\\
0\end{pmatrix} : r,s \in R \}$

$U_5 = \{ \begin{pmatrix}
r\\
s\\
1\end{pmatrix} : r,s \in R \}$

$U_6 = \{ \begin{pmatrix}
r\\
s\\
0\end{pmatrix} : r,s,t \in R \text{ and } r+s+t=1 \}$

$U_7 = U_1 \cap U_2$

$U_8 = U_1 \cup U_2$

a) For each of the 8 sets sat whether it is a subspace, and briefly explain your answer.

b) For each of the 8 sets, classify it as one of
i. A line passing through the origin.
ii. A line not passing through the origin.
iii. A plane passing through the origin.
iv. A plane not passing through the origin.
v. none of the above

c) What do you conclude about the subspaces of $R^3$?
• October 13th 2008, 11:20 AM
I Congruent
I am not too confident with my answers and im completely stuck on part b)