# HW4 - Jolley Garrett – Homework 4 – Due 3:00 am –...

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Unformatted text preview: Jolley, Garrett – Homework 4 – Due: Sep 19 2007, 3:00 am – Inst: R Heitmann 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Find the value of lim x → 2 • f ( x ) g ( x )- 2 6 f ( x )- 1 g ( x ) ‚ when lim x → 2 f ( x ) = 8 , lim x → 2 g ( x ) =- 3 . Correct answer:- . 509804 . Explanation: By properties of limits, lim x → 2 µ f ( x ) g ( x )- 2 6 f ( x )- 1 g ( x ) ¶ = lim x → 2 ( f ( x ) g ( x )- 2) lim x → 2 (6 f ( x )- 1 g ( x )) . But again by properties of limits, lim x → 2 ( f ( x ) g ( x )- 2) = ‡ lim x → 2 f ( x ) ·‡ lim x → 2 g ( x ) ·- 2 , while lim x → 2 (6 f ( x )- 1 g ( x )) = 6 ‡ lim x → 2 f ( x ) ·- 1 ‡ lim x → 2 g ( x ) · . Consequently, limit =- 24- 2 48 + 3 =- 26 51 ≈ - . 509804 . keywords: limit, laws of limits 002 (part 1 of 1) 10 points Below are the graphs of functions f and g . 4 8- 4 4 8- 4- 8 f : g : Use these graphs to determine lim x → 3 { f ( x ) + g ( x ) } . 1. limit does not exist 2. limit = 3 correct 3. limit =- 2 4. limit = 6 5. limit = 1 Explanation: From the graph it is clear that lim x → 3 { f ( x ) + g ( x ) } = 3 . (Don’t forget that for a limit to exist at a point, the left and right hand limits have to exist and coincide. So determine left and right hand limits separately and use limit laws.) keywords: limit of sum of functions, graph, limit 003 (part 1 of 1) 10 points Determine lim x → 3 n 3 x 2- 3 x- 1 x- 3 o . Jolley, Garrett – Homework 4 – Due: Sep 19 2007, 3:00 am – Inst: R Heitmann 2 1. limit =- 3 2. limit = 1 2 3. limit = 3 4. limit =- 1 3 correct 5. limit =- 1 2 6. limit does not exist 7. limit = 1 3 Explanation: After simplification we see that 3 x 2- 3 x- 1 x- 3 = 3- x x ( x- 3) =- 1 x for all x 6 = 3. Thus limit =- lim x → 3 1 x =- 1 3 . keywords: analytic limit, difference rational functions, limit, common denominators 004 (part 1 of 1) 10 points Determine if lim x → 0+ 5- (4 / √ x ) 5- (1 / √ x ) exists, and if it does, find its value. 1. limit does not exist 2. limit =- 1 4 3. limit = 4 correct 4. limit =- 4 5. limit = 1 4 Explanation: After simplification and cancellation 5- (4 / √ x ) 5- (1 / √ x ) = 5 √ x- 4 5 √ x- 1 . On the other hand, lim x → 0+ √ x = 0 , and so 5 √ x- 4 5 √ x- 1 = 4 by Properties of Limits. Consequently, the given limit exists and limit = 4 . keywords: analytic limit, quotient radicals, keywords: 005 (part 1 of 1) 10 points Determine if lim x → 3+ p 16- x 2 exists, and if it does, find its value. 1. limit = 3 2. limit = 0 3. limit does not exist 4. limit = √ 10 5. limit = 4 6. limit = √ 7 correct 7. limit = 3 Explanation: For x near 3 the inequality 16- x 2 > holds, so f ( x ) = p 16- x 2 Jolley, Garrett – Homework 4 – Due: Sep 19 2007, 3:00 am – Inst: R Heitmann 3 is well defined for such x . Consequently, by Properties of Limits, the right hand limit...
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HW4 - Jolley Garrett – Homework 4 – Due 3:00 am –...

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