Assignment 1 Query

course Mth 151

assignment #001001. `Query 1

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College Algebra

01-22-2008

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09:00:56

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: 3

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09:01:07

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

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RESPONSE -->

ok

self critique assessment: 3

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09:01:52

query 2.1.24 set builder for set of presidents between LBJ and Clinton

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RESPONSE -->

I am not sure who the Presidents are between these two.

confidence assessment: 0

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09:02:53

** 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 -->

I was looking for a specific answer but I see that I was only supposed to provide the variables.

self critique assessment: 2

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09:03:25

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

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RESPONSE -->

finite because it ends

confidence assessment: 3

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09:05:43

** 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 -->

My thinking was along the line of you having the number 0 and 1 and that is it but I understand that there are an infinite set of numbers between 0 and 1 like 1/2,1/3,etc.

self critique assessment: 2

Good thinking. We could get both perspectives by saying that the set is bounded (by the two ends of the interval) but infinite since the interval contains an infinite set of points.

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09:10:02

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) is one because it is saying how many are in the set.

confidence assessment: 3

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09:11:11

** 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 had the right idea but I did not get the right response because I thought it was asking for one senator but it was asking how many out of all the senators in our country.

self critique assessment: 2

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09:11:51

query 2.1.54 {x|x is neagtive number}

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RESPONSE -->

{-1,-2,-3,-4.....}

confidence assessment: 3

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09:12:48

** 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 -->

I did not identify whether the set was well -defined or not. I just provided the set notation.

self critique assessment: 2

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09:13:00

2.1.72 true or false 2 not subset of {7,6,5,4}

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RESPONSE -->

true

confidence assessment: 3

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09:13:30

** 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 -->

ok

self critique assessment: 3

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09:14:32

2.1.84 C={4,10,12}, B={2,4,8,10}

Is it true or false that every element of C is also an element of B?

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RESPONSE -->

That is not true because C also contains the element of 12 which is not in B

confidence assessment: 3

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09:14:40

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

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RESPONSE -->

ok

self critique assessment: 3

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