Math51open

#$&*

course Mth 151

4/30/2101 10:13

022.  `query 22 

 

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Question:  `q4.6.9 {-1,0,1} group on multiplication?

 

 

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Your solution:

This system is not a group because, not all of the elements have an inverse. -1's inverse is -1 because -1 * -1 = 1, 1's inverse is 1 because 1 * 1 = 1, but 0 doesn’t have an inverse because noting can be multiplied by it to get 1.

 

 

confidence rating #$&*: 3

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Given Solution: 

`a** There are four criteria for the group: closure, identity, inverse property, and associativity.

 

The lack of any one of these properties means that the set and operation do not form a group.

 

The set is closed on multiplication.

 

The identity is the element that when multiplied by other elements does not change them.   The identity for this operation is 1, since 1 * -1 = -1, 1 * 0 = 0 and 1 * 1 = 1.

 

Inverses are pairs of elements that give you 1 when you multiply them.  For example -1 * -1 = 1 so -1 is its own inverse.  1 * 1 = 1 so 1 is also its own inverse.  However, 0 does not have an inverse because there is nothing you can multiply by 0 to get 1.

 

Since there is an element without an inverse this is not a group.  **

 

 

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Self-critique (if necessary): OK

 

 

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Self-critique Rating: OK

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Question:  `q4.6.25  verify (NT)R = N(TR)

 

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Your solution: 

(NT)R = VR = M and N(TR) = NP = M, M = M so the statement it verified.

 

 

confidence rating #$&*: 3

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Given Solution: 

`a** From the table

 

(NT)R= V R = M

 

and

 

N(TR)= N  P = M

 

This verifies the identity. **

 

 

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Self-critique (if necessary): OK

 

 

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Self-critique Rating: OK

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Question:  `qquery 4.6.33  inverse of T

 

 

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Your solution: 

The inverse of T would be T because TT is the identity.

 

 

confidence rating #$&*: 3

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Given Solution: 

`a** T is its own inverse because T T gives you the identity **

 

 

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Self-critique (if necessary): OK

 

 

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Self-critique Rating: OK

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Question:  `q4.6.42.  Explain what property is gained when the system of integers is extended to the system of rational numbers.

 

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Your solution: 

The inverse property is gained when a system of integers is extended to the system of rational numbers.

 

 

confidence rating #$&*: 2

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Given Solution: 

`a** The set of integers is a group on addition, with identity 0 and every number x having additive inverse -x.

 

It is not a group on multiplication. It contains the identity 1 but does not contain inverses, except for 1 itself. This is because, for example, there is no integer you can multiply by 2 to get the identity 1.

 

If we extend the integers to the rational numbers we do get the inverses. The inverse of 2 is 1/2 since x * 1/2 = 1, the identity. In general the multiplicative inverse of x is 1 / x.

 

However we still don't have a group on multiplication since 0 still doesn't have an inverse, 1 / 0 being undefined on the real numbers. **

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Self-critique (if necessary):

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Self-critique rating:

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Question:  `q4.6.42.  Explain what property is gained when the system of integers is extended to the system of rational numbers.

 

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Your solution: 

The inverse property is gained when a system of integers is extended to the system of rational numbers.

 

 

confidence rating #$&*: 2

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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Given Solution: 

`a** The set of integers is a group on addition, with identity 0 and every number x having additive inverse -x.

 

It is not a group on multiplication. It contains the identity 1 but does not contain inverses, except for 1 itself. This is because, for example, there is no integer you can multiply by 2 to get the identity 1.

 

If we extend the integers to the rational numbers we do get the inverses. The inverse of 2 is 1/2 since x * 1/2 = 1, the identity. In general the multiplicative inverse of x is 1 / x.

 

However we still don't have a group on multiplication since 0 still doesn't have an inverse, 1 / 0 being undefined on the real numbers. **

"

Self-critique (if necessary):

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Self-critique rating:

#*&!

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Question:  `q4.6.42.  Explain what property is gained when the system of integers is extended to the system of rational numbers.

 

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Your solution: 

The inverse property is gained when a system of integers is extended to the system of rational numbers.

 

 

confidence rating #$&*: 2

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution: 

`a** The set of integers is a group on addition, with identity 0 and every number x having additive inverse -x.

 

It is not a group on multiplication. It contains the identity 1 but does not contain inverses, except for 1 itself. This is because, for example, there is no integer you can multiply by 2 to get the identity 1.

 

If we extend the integers to the rational numbers we do get the inverses. The inverse of 2 is 1/2 since x * 1/2 = 1, the identity. In general the multiplicative inverse of x is 1 / x.

 

However we still don't have a group on multiplication since 0 still doesn't have an inverse, 1 / 0 being undefined on the real numbers. **

"

Self-critique (if necessary):

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Self-critique rating:

#*&!#*&!

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Question:  `q4.6.42.  Explain what property is gained when the system of integers is extended to the system of rational numbers.

 

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Your solution: 

The inverse property is gained when a system of integers is extended to the system of rational numbers.

 

 

confidence rating #$&*: 2

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution: 

`a** The set of integers is a group on addition, with identity 0 and every number x having additive inverse -x.

 

It is not a group on multiplication. It contains the identity 1 but does not contain inverses, except for 1 itself. This is because, for example, there is no integer you can multiply by 2 to get the identity 1.

 

If we extend the integers to the rational numbers we do get the inverses. The inverse of 2 is 1/2 since x * 1/2 = 1, the identity. In general the multiplicative inverse of x is 1 / x.

 

However we still don't have a group on multiplication since 0 still doesn't have an inverse, 1 / 0 being undefined on the real numbers. **

"

Self-critique (if necessary):

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Self-critique rating:

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&#Very good responses. Let me know if you have questions. &#