course Mth 151 e]orÈCwassignment #022
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18:49:30 4.5.9 {-1,0,1} group on multiplication?
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RESPONSE --> -1 0 1 -1 1 0 -1 0 0 0 0 1 -1 0 1 This group is closed. The identity is 1, because any number multiplied by 1 remains the same. -1 * -1 =1 1 * 1= 1 0 * 0 =0 Because 0 doesn't have an inverse, this system isn't a group. confidence assessment: 3
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18:49:43 ** 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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RESPONSE --> OK self critique assessment: 3
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18:51:07 4.5.25 verify (NT)R = N(TR)
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RESPONSE --> (NT)R = N(TR) (NT)R: NT = V VR = M N(TR): TR = P PN = M The statement is true. confidence assessment: 3
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18:51:14 ** From the table (NT)R= V R = M and N(TR)= N P = M This verifies the identity. **
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RESPONSE --> OK self critique assessment: 3
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18:51:48 query 4.5.33 inverse of T
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RESPONSE --> According to the table, T is its own inverse. The identity is Q, and TT=Q confidence assessment: 3
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18:51:53 ** T is its own inverse because T T gives you the identity **
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RESPONSE --> OK self critique assessment: 3
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18:53:10 4.5.42. Explain what property is gained when the system of integers is extended to the system of rational numbers.
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RESPONSE --> The inverse property is gained, because you no longer have to use only whole numbers. An integer multiplied by a rational number can produce the inverse, which is 1. The only number where an inverse can't be produced is 0, because 0 multiplied by any number is still 0. confidence assessment: 3
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18:53:19 ** 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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RESPONSE --> OK self critique assessment: 3
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