Lesson 20.

NOTE 1: Be sure to read Homework Format and Homework Writing Policy BEFORE writing up your solutions to be turned in.

NOTE 2: When two or more Lessons are to be turned in on the same day, please staple the Lessons separately and turn them in separately.

Due Monday, February 25

Sect. 6:
6.11(a)*(d)**,  6.27(b)(d)***

*   For 6.11(a), give precise proofs or counterexamples. The proofs should be given in the standard way for proving universally quantified statements.
NOTE: The statement  “x  divides  y”  means (in this context)  “there exists a natural number  k  such that  y = kx”.  (Note that the definition of  “divides” contains no reference to “division”.  It is purely a multiplicative property:  “x divides y”  means the same as  “x is a factor of y”,  which is the same as  “y is a multiple of x”.)
PLEASE READ, UNDERSTAND, AND DIGEST THE PRECEDING DEFINITION!

**  For 6.11(d), think only about reflexive and symmetric at this time (transitive may be dealt with in a later lesson). Give a complete proof; since this set consists of a small number of specific elements, you will be dealing with them specifically.

***For 6.27(b)(d), give a precise proof or counterexample. A proof should be given in the standard way for proving universally quantified statements.

NOTE: As stated on the Course Home Page, all due dates are tentative. Assignments, or parts of assignments, may be postponed to a later date.


Last modified Feb 25, 2008 9:09 PM

Go to Lesson 21 (due Feb 25).

Go to Lesson 20a (due Feb 29).

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