2-1 query

course Mth 151

7/12 11

If your solution to stated problem does not match the given solution, you should self-critique per instructions at

http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm

Your solution, attempt at solution. If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not understand about it. This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

001. `Query 1

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Question: `qQuery 2.1.12 counting #'s 4 to 14

List the elements of the set.

 

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Your solution:

{5,6,7,8,9,10,11,12,13,14,15,16,17}

confidence rating #$&* 3

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Given Solution:

`a**A list of the elements would just be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. **

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Self-critique (if necessary):

I used the listing method using the braces outside the set. Is is unnecesary to use braces when not asked to use any method?

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Self-critique rating #$&*2

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Question: `qquery 2.1.24 listing for set of presidents between LBJ and Clinton

 

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Your solution:

{Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Reagan, George Bush, Bill Clinton}

confidence rating #$&* 3

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Given Solution:

`a** A listing would be {}{}{Lyndon Johnson, Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Regan, George HW Bush, William Clinton}.{}{}Set-builder notation is {x|x is a president who served between Lyndon Johnson and William Clinton}

x is a variable and the condition 'x is a president who served between Lyndon Johnson and William Clinton' tells you what possible things the variable can be.

COMMON ERROR: It's incorrect to say {x | x is the set of presidents who served between Johnson and Clinton}.

x is a president, not a set of presidents. Should be {x|x is a president who served between Lyndon Johnson and William Clinton} **

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Self-critique (if necessary):

When you used the listing method you listed Lyndon Johnson First; is that correct? I thought he would be outside the set because it asked for after and before.

The word 'between' has an ambiguous meaning.

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Self-critique rating #$&*2

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Question: `q2.1.40 finite or infinite: set of rat #'s 0 to 1

 

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Your solution:

Rational numbers are p/q where p and q are integers and q is not equal to 0. So the set of numbers between 0 and 1 is infinite.

confidence rating #$&* 3

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Given Solution:

`a** Rational numbers have form p/q, where p and q are integers. Numbers like 5/8, 57/31, -3/5, -57843/7843, etc.

The subset {1/2, 1/3, 1/4, 1/5, ... } is just by itself an infinite set of rational numbers between 0 and 1.

Then you have things like 348/937, and 39827389871 / 4982743789, and a whole infinite bunch of others. There are thus infinitely many rational numbers in any interval of the real line.

COMMON MISCONCEPTION: finite, because it doesn't go on forever

Rational numbers have form p/q, where p and q are integers. Numbers like 5/8, 57/31, -3/5, -57843/7843, etc. Not all of these lie between 0 and 1, of course. **

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Self-critique (if necessary):ok

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Self-critique rating #$&*3

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Question: `q2.1.48 n(A), A={x|x is a U.S. senator}

What is n(A) and why?

 

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Your solution:

n(A) is the number of elements in a set called the cardinal number

there are 100 U.S. senators so A=100

confidence rating #$&* 3

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Given Solution:

`a** n(A) stands for the number of elements in the set--in this case for the number of senators. There are 100, 2 from each State. So n(A) = 100. **

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Self-critique (if necessary):ok

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Self-critique rating #$&*3

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Question: `qquery 2.1.54 {x|x is neagtive number}

 

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Your solution:

Well defined because we can easily tell whether a number is part of the set by whether or not it is a negative number.

confidence rating #$&* 3

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Given Solution:

`a** This notation means all possible values of x such that x is a negative number.

The question is whether the set is well-defined or not.

It is in fact well-defined because there is a definite way to decide whether a given object is an element of the set, because there is a definite way to determine whether an object is a negative number or not.

ALTERNATIVE ANSWER: The set is well-defined because you have a criterion by which you can definitely decide whether something is or is not in the set. **

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Self-critique (if necessary):ok

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Self-critique rating #$&*3

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Question: `q2.1.74 (formerly 2.1.72) This was not assigned, but you should be able to answer based on your work on similar problems: It is or is it not true that 2 is not not subset of {7,6,5,4}?

 

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Your solution:

It is true that 2 is not a subset of {7,6,5,4} because it is not even part of the set.

confidence rating #$&* 3

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Given Solution:

`a** The statement is that 2 is not a subset. The statement is true because 2 isn't even a set, it's just a number. {2} is a set and could be a subset of something. 2 is just a number; it isn't a set so it can't be a subset of anything.

The usual answer is that 2 isn't a subset because 2 isn't in the set. However that's not the correct reason. The correct reason is that 2 isn't a set and a subset must be a set.

COMMON MISCONCEPTION: the statement says that 2 is not a subset, not that it is not an element of the set. So the reason it's not a subset is that 2 isn't a set at all, so it can't be a subset of anything. **

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Self-critique (if necessary):ok

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Self-critique rating #$&*3

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Question: `q2.1.86 (formerly 2.1.84). This was not assigned but you did answer several questions related to the sets C={4,10,12}, B={2,4,8,10}, and should be able to answer this.

Is it true or false that every element of C is also an element of B? Be sure to include your reasoning.

 

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Your solution:

This question is actually #88.

False because C contains the element 12 and B doesn’t.

#86. 8 is not an element of B is false

confidence rating #$&* 3

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Given Solution:

`a** Specifically it's false because the element 12 is in C but not in B. **

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&#Good work. See my notes and let me know if you have questions. &#

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