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Unformatted text preview: TA: Yankun Wang Econ 617 Problem Set 2 Solution Key 1. [Linear Dependence and Independence] (a) Let S = { e 1 , e 2 , e 3 } be the set of unit vectors in R 3 . Let T = { x 1 , x 2 , x 3 } be a set of vectors in R 3 , de f ned by: x 1 = e 1 + e 2 , x 2 = e 2 + e 3 , x 3 = e 3 + e 1 Is T a set of linearly independent vectors in R 3 ? Explain. Solution: Claim: T is a set of linearly independent vectors in R 3 . Proof: Suppose there exists 1 , 2 and 3 such that: 1 x 1 + 2 x 2 + 3 x 3 = 0 , i.e. : 1 1 1 + 2 1 1 + 3 1 1 = . 1 + 3 1 + 2 2 + 3 = 1 = 0; 2 = 0; 3 = 0 . Thus by de f nition, T is a set of linearly independent vectors in R 3 . (b) Let S = { e 1 , e 2 , e 3 } be the set of unit vectors in R 3 . Let T = { x 1 , x 2 , x 3 } be a set of vectors in R 3 , de f ned by: x 1 = e 1 , x 2 = e 1 + 2 e 2 , x 3 = e 1 + 2 e 2 + 3 e 3 Is T a set of linearly independent vectors in R 3 ? Explain....
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 Fall '08
 STAFF

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