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Unformatted text preview: Solutions homework 1. (1) Prove that [ 1; 1) is not compact by using the definition of a compact set (to get credit for the problem, use the definition and not any theorems about compact sets). Proof: Let O n = ( 1 , 1 1 n ). Then [ 1; 1) ⊂ ∪ n O n , but [ 1; 1) can’t be covered by ∪ N n =1 O n for any N , as 1 1 2 N / ∈ ∪ N n =1 O n . (2) What is an interior point? Prove that 1 4 is an interior point of (0; 2]. Proof: p is an interior point of E if there exists > 0 such that ( p ,p + ) ⊂ E . Let = 1 4 . Then ( 1 4 , 1 4 + ) = (0 , 1 2 ) ⊂ (0; 2]. (3) Let a 1 = √ 6 and a n +1 = √ 6 + a n for n ≥ 1. a. Show that a n ≤ 3 for all n ≥ 1. For n = 1 we have a 1 = √ 6 ≤ √ 9 = 3. Assume now that a n ≤ 3. Then a n +1 = √ 6 + a n ≤ √ 6 + 3 = 3. Hence by induction a n ≤ 3 for all n ≥ 1. b. Show that { a n } is an increasing sequence. For n = 1 we get a 2 = p 6 + √ 6 ≥ √ 6 = a 1 . Assume now that a n +1 ≥ a n . Then a n +2 = √ 6 + a n +1...
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This note was uploaded on 02/05/2012 for the course MATH 555 taught by Professor Staff during the Spring '07 term at South Carolina.
 Spring '07
 Staff
 Sets

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