HwLectures 6 and 7 - MAT 1341A These are the solutions to the practice assignment Don’t read these until you have attempted the questions on your

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Unformatted text preview: MAT 1341A: These are the solutions to the practice assignment. Don’t read these until you have attempted the questions on your own! Question # 1: (a) Determine whether 4 8 1 ∈ span 2 1- 3 5 , 2- 1 3 ⊆ R 4 . Solution: We need to try to solve: 4 8 1 = a 2 1- 3 5 + b 2- 1 3 for some a, b ∈ R . This gives the following 4 linear equations: 2 a = 4 , a + 2 b = 8 ,- 3 a- b = 0 , 5 a + 3 b = 1 The first gives a = 2, so the second implies b = 3. But plugging this into the third equation gives a contradiction. So we conclude this system cannot be solved. Hence, our answer is NO. (b) Determine whether 10 6- 8 22 ∈ span 1 2 3 , 1- 2 1 ⊆ M 2 , 2 . Solution: We need to try to solve: 10 6- 8 22 = a 1 2 3 + b 1- 2 1 for a, b ∈ R . Equating terms in each component gives the four equations: a + b = 10 , 2 a = 6 ,- 2 b =- 8 , 3 a + b = 22 The second gives a = 3 and the third gives b = 4, which fails the first equation, so there is no solution, and again our answer is NO. Question # 2: Let P 1 be the vector space of all polynomials with degree ≤ 1. Show that any element of P 1 is in the span of the polynomials x- 2, 2 x + 1, and 2. ( Hint: take an arbitrary element of P 1 , which looks like ax + b for a, b ∈ R , and see if you can write it as a linear combination of these vectors. ) Solution: We need to decide if, for any ax + b...
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This note was uploaded on 09/28/2011 for the course MATH 1341 taught by Professor Daigle during the Winter '10 term at University of Ottawa.

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HwLectures 6 and 7 - MAT 1341A These are the solutions to the practice assignment Don’t read these until you have attempted the questions on your

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