Is W a Subspace of All Ordered Pairs?

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Homework Help Overview

The discussion revolves around the set W, defined as the set of all ordered pairs of real numbers, and the operations of addition and scalar multiplication applied to this set. Participants are exploring whether W can be considered a subspace of a vector space, particularly focusing on the implications of its defined operations.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are examining the closure of W under scalar multiplication and questioning the nature of the operations defined on W. There is a discussion about whether the operation kU=(0, ku2) results in an ordered pair of real numbers and whether W contains the zero vector.

Discussion Status

Some participants have provided insights into the definitions and implications of being closed under scalar multiplication, while others are questioning the foundational assumptions about W as a subset of a vector space. The conversation appears to be productive, with clarifications being offered regarding the definitions of subspaces.

Contextual Notes

There is an ongoing discussion about the lack of restrictions on W and the implications of its operations, as well as the need to verify the eight vector space axioms to determine if W can be classified as a vector space.

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Homework Statement

Let W be the set of all ordereed pairs of real numbers, and consider the following addition and scalar multiplication operations on U=(u1,u2) and V=(v1,v2)

U+V is standard addition but kU=(0, ku2)

Homework Equations

Is W closed under scalar multiplication?

The Attempt at a Solution

I understand that W is not a vector space but my book suggests that it is a subspace closed by scalar multiplication.

Is it because kU=(k0, ku2) where k multiplies both terms?
 
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Being closed under scalar multiplication just means that if w \in W and k \in \mathbb{R} then k w \in W.
Since W doesn't really have any restrictions, you only need to check that (0, ku2) is an ordered pair of real numbers.
 
Is kU \, = \, (0, ku_{2}) an ordered pair of reals ? Also, does W contain the zero vector ?
 
It's pretty strange to talk about subspaces here, since W isn't defined as a subset of a vector space. It's just defined as a set with two operations which may or may not turn it into a vector space.

If it turns out to be closed under both addition and (this non-standard) scalar multiplication, then you can check if it satisfies the eight vector space axioms, to see if it's a vector space.
 
Thanks for the help! That solves it for me completely! I thoroughly didn't understand the definitions of subspace and what they mean and represent, so this simple explanation really clears up a big misconception that I had.
 

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