MAT 2401 Linear Algebra 4.4 Spanning Sets and Linear Independence
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HW WebAssign 4.4 Part I No Written Homework
Preview Continue to examine the structure of vector spaces.
Questions What is the “size” of a vector space? Is R 2 “smaller” than R 3 ? Why? Is R 2 “smaller” than P 2 ? Why?
Answers To answer these questions, we need to look into a few things… Linear Combination (4.4) Spanning Set (4.4) Linear Independence (4.4) Basis (4.5) Dimension (4.5)
Answers To answer these questions, we need to look into a few things… Linear Combination (4.4) Not new Spanning Set (4.4) Linear Independence (4.4) ???? Basis (4.5) Dimension (4.5)
Linear Combination
Example 0
Example 0 (a)
Example 0 (b)
Example 0 (c)
Example 0 We used trial-and-error in this example. It will not work for more complicated vector spaces. We will illustrate a systematic method in the examples below.
Linear Combination
Example 1 Determine whether u=(3,1,0) can be written as a linear combination of v 1 =(1,1,2), v 2 =(1,0,-1), and v 3 =(-5,-2,-1).
Q&A Q: What happens to the GJ elimination if u is not a linear combination of v 1, v 2, and v 3. A:
Spanning Set
Example 0
Example 2 Let S={(1,0,0), (0,1,0), (0,0,1)} Determine whether S spans R 3.
Example 3 Let S={1, x, x 2 } Determine whether S spans P 2.
Example 4 Let S={(1,1,4), (1,0,3), (0,1,1)} Determine whether S spans R 3.
The Span of a Subset
Example 5 Let S={(1,0,0), (0,1,0)} R 3. Interpret the geometric meaning of span(S).