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Unformatted text preview: 18.100B Midterm Exam Tuesday, October 7 2008, 7:30–9:00, in 4–370. Closed book, no calculators. YOUR NAME: YOUR SECTION (circle one): 18.100B MWF 121 18.100B TR 12:30 18.100C This is a 90minute evening exam. No notes, books, or calculators are permitted. Point values are indicated for each problem. Do all the work on these pages. (Use the back sides if needed.) GRADING 1. /25 2. /20 3. /20 4. /20 5. /20 6. /25 TOTAL /130 Problem 1. [25 points: (a) /5 (b) /10 (c) /5 (c) /5 ] (a) Define what a metric is. (b) Let d : R n × R n → R be defined by d ( x , y ) =  x 1 − y 1  + 2  x 2 − y 2  + ··· + n  x n − y n  . Here x = ( x 1 , x 2 , . . ., x n ) and y = ( y 1 , y 2 , . . ., y n ) . Prove that d is a metric. (c) Sketch the unit ball of d in R 2 : that is, the set of all x ∈ R 2 such that d ( x , ) < 1 . (d) Let g : R 2 × R 2 → R be defined by g ( x , y ) =  x 1 − y 2  . Is g a metric? Prove your claim. Problem 2. [20 points: (a) /5 (b) /5 (c) /10 ] Consider the following sequences of real numbers:...
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This note was uploaded on 12/07/2011 for the course MATH 18.100B taught by Professor Prof.katrinwehrheim during the Fall '10 term at MIT.
 Fall '10
 Prof.KatrinWehrheim

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