qub070918

course mth 151

£Ö[ôÐÖªÁî¹ùÃÃço÷ÜÚÜǬӚL͈ôå²assignment #001

001. `Query 1

College Algebra

10-17-2007

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11:05:18

Query 2.1.12 counting #'s 4 to 14

List the elements of the set.

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RESPONSE -->

{4,5,6,7,8,9,10,11,12,13,14}

confidence assessment: 2

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11:05:30

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

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RESPONSE -->

okay

self critique assessment: 2

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11:06:53

query 2.1.24 listing for set of presidents between LBJ and Clinton

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RESPONSE -->

{LBJ,Nixon,Ford,Carter,Reagan,Bush,Clinton}

confidence assessment: 2

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11:07:27

** 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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RESPONSE -->

okay

self critique assessment: 2

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11:09:43

2.1.40 finite or infinite: set of rat #'s 0 to 1

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RESPONSE -->

finite, the number could be cosidered to be infinite,because some of the numbers could possible be infinite or have no ending. But looking at what is asked there is a set begining and end, giving me to conclusion of finite.

confidence assessment: 2

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11:11:08

** 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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RESPONSE -->

i think i had some what of a correct thought, i found my error in the definiation of rational numbers, but i feel comfortable with finite and infinite numbers

self critique assessment: 2

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11:21:17

2.1.48 n(A), A={x|x is a U.S. senator}

What is n(A) and why?

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RESPONSE -->

n(A)= the number of elements in a set.

n(A)= 50

confidence assessment: 2

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11:22:07

** 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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RESPONSE -->

I was wrong on my civic's, but understood the definiation of n(A)

self critique assessment: 2

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11:23:38

query 2.1.54 {x|x is neagtive number}

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RESPONSE -->

This would be well definined. The problem is asking for a definined group that is in a set

confidence assessment: 2

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11:24:00

** 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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RESPONSE -->

okay

self critique assessment: 2

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11:25:33

2.1.74 (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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RESPONSE -->

2 is not a subset, because 2 is not listed in the set at all.

confidence assessment: 2

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11:27:27

** 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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RESPONSE -->

I feel into the catagory of 2 is not a set because 2 is not listed. I didn't explain that in order for a listing of a group to be a subset is first must be part of a set.

self critique assessment: 2

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11:28:56

2.1.86 (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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RESPONSE -->

The statement is false.

not all elemnts of c are found in b.

for example 12 is found in c, but not in b.

confidence assessment: 2

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11:29:08

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

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RESPONSE -->

okay

self critique assessment: 2

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Your work looks very good. Let me know if you have any questions. &#