Page 1
Edurev123
3. Fields
3.1 Consider the polynomial ring ?? [?? ]. Show ?? (?? )=?? ?? -?? is irreducible over ?? .
Let ?? be the ideal in ?? [?? ] generated by ?? (?? ) . Then show that ?? [?? ]/?? is a field and
that each element is of the form ?? ?? +?? ?? ?? +?? ?? ?? ?? with ?? ,?? ?? ,?? ?? in ?? and ?? =?? +?? .
(2010 : 15 Marks)
Solution:
Given :
?? (?? )=?? 3
-2
Let ?? (?? ),?? (?? )??? [?? ], and ?? (?? ) is reducible such that
?? (?? ) =?? (?? )·?? (?? )
Suppose, ?? (?? ) =?? +?? ? ?? (?? ) =?? 2
+?? ?? +?? ???? (?? ) =?? 3
-2=(?? +?? )(?? 2
+???? +?? )
? ?? 3
-2 =?? 3
+?? ?? 2
+???? +?? ?? 2
+???? +????
Comparing LHS & RHS, we get
?? +?? ?=0??? =-?? ???? +?? ?=0
??-?? 2
+?? ?=0??? =?? 2
???? ?=-2
???? 3
?=-2??? =-2
1/3
which is not a rational number
i.e., ?? ??? ??? ,?? ???
??? (?? ) is irreducible over ?? .
Now, ?? is ideal generated by ?? (?? )
i.e.,
?? =??? (?? )?
?
?? (?? )
?? is a field as ?? (?? ) is irreducible (theorem)
Page 2
Edurev123
3. Fields
3.1 Consider the polynomial ring ?? [?? ]. Show ?? (?? )=?? ?? -?? is irreducible over ?? .
Let ?? be the ideal in ?? [?? ] generated by ?? (?? ) . Then show that ?? [?? ]/?? is a field and
that each element is of the form ?? ?? +?? ?? ?? +?? ?? ?? ?? with ?? ,?? ?? ,?? ?? in ?? and ?? =?? +?? .
(2010 : 15 Marks)
Solution:
Given :
?? (?? )=?? 3
-2
Let ?? (?? ),?? (?? )??? [?? ], and ?? (?? ) is reducible such that
?? (?? ) =?? (?? )·?? (?? )
Suppose, ?? (?? ) =?? +?? ? ?? (?? ) =?? 2
+?? ?? +?? ???? (?? ) =?? 3
-2=(?? +?? )(?? 2
+???? +?? )
? ?? 3
-2 =?? 3
+?? ?? 2
+???? +?? ?? 2
+???? +????
Comparing LHS & RHS, we get
?? +?? ?=0??? =-?? ???? +?? ?=0
??-?? 2
+?? ?=0??? =?? 2
???? ?=-2
???? 3
?=-2??? =-2
1/3
which is not a rational number
i.e., ?? ??? ??? ,?? ???
??? (?? ) is irreducible over ?? .
Now, ?? is ideal generated by ?? (?? )
i.e.,
?? =??? (?? )?
?
?? (?? )
?? is a field as ?? (?? ) is irreducible (theorem)
???
?? (?? )
?? =??? (?? )>+?? 0
+?? 1
?? +?? 2
?? 2
=?? +?? 0
+?? 1
?? +?? 2
?? 2
deg·(?? 0
+?? 1
?? +?? 2
?? 2
)<deg·(?? (?? ))
?????????????????????
remainder term
where ?? 0
,?? 1
,?? 2
??? . Now,
?? ?=?? +?? ?? 0
+?? 1
?? +?? 2
?? 2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )
2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )(?? +?? )
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? 2
+?? )
?=?? 0
+?? 1
?? +?? 2
?? 2
+?? which is equivalent to eqn. (1)
?
?? (?? )
?? can be written as ?? 0
+?? 1
?? +?? 2
2
2
where ?? =?? +?? .
3.2 Show that the set of matrices ?? ={[
?? -?? ?? ?? ]?? ,?? ??? } is a field under the usual
binary operations of matrix addition and matrix multiplication. What are the
additive and multiplicative identities and what is the inverse of [
?? -?? ?? ?? ] ? Consider
iiie map ?? :?? ??? defined by ?? (?? +???? )=[
?? -?? ?? ?? ]. Show that ?? is an isomorphism
(Here ?? is the set of real numbers and ?? is the set of complex numbers)?
(2013 : 10 Marks)
Solution:
Approach : Prove only the important parts in actual exam.
SCM?(2,?? ) where ?? (?? ,?? ) is the ring of 2×2 matrices with entries from ?? .
To show ?? is a field
and
[
?? -?? ?? ?? ]??? ?[
?? -?? ?? ?? ]
-1
=[
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]
-1
??? [
?? -?? ?? ?? ][
?? -?? ?? ?? ]
-1
=[
?? -?? ?? ?? ][
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]=[
???? +????
?? 2
+?? 2
-(???? -???? )
?? 2
+?? 2
???? -????
?? 2
+?? 2
???? +????
?? 2
+?? 2
]???
So, ?? is closed w.r.t. multiplication and has multiplicative inverse.
Also,
Page 3
Edurev123
3. Fields
3.1 Consider the polynomial ring ?? [?? ]. Show ?? (?? )=?? ?? -?? is irreducible over ?? .
Let ?? be the ideal in ?? [?? ] generated by ?? (?? ) . Then show that ?? [?? ]/?? is a field and
that each element is of the form ?? ?? +?? ?? ?? +?? ?? ?? ?? with ?? ,?? ?? ,?? ?? in ?? and ?? =?? +?? .
(2010 : 15 Marks)
Solution:
Given :
?? (?? )=?? 3
-2
Let ?? (?? ),?? (?? )??? [?? ], and ?? (?? ) is reducible such that
?? (?? ) =?? (?? )·?? (?? )
Suppose, ?? (?? ) =?? +?? ? ?? (?? ) =?? 2
+?? ?? +?? ???? (?? ) =?? 3
-2=(?? +?? )(?? 2
+???? +?? )
? ?? 3
-2 =?? 3
+?? ?? 2
+???? +?? ?? 2
+???? +????
Comparing LHS & RHS, we get
?? +?? ?=0??? =-?? ???? +?? ?=0
??-?? 2
+?? ?=0??? =?? 2
???? ?=-2
???? 3
?=-2??? =-2
1/3
which is not a rational number
i.e., ?? ??? ??? ,?? ???
??? (?? ) is irreducible over ?? .
Now, ?? is ideal generated by ?? (?? )
i.e.,
?? =??? (?? )?
?
?? (?? )
?? is a field as ?? (?? ) is irreducible (theorem)
???
?? (?? )
?? =??? (?? )>+?? 0
+?? 1
?? +?? 2
?? 2
=?? +?? 0
+?? 1
?? +?? 2
?? 2
deg·(?? 0
+?? 1
?? +?? 2
?? 2
)<deg·(?? (?? ))
?????????????????????
remainder term
where ?? 0
,?? 1
,?? 2
??? . Now,
?? ?=?? +?? ?? 0
+?? 1
?? +?? 2
?? 2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )
2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )(?? +?? )
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? 2
+?? )
?=?? 0
+?? 1
?? +?? 2
?? 2
+?? which is equivalent to eqn. (1)
?
?? (?? )
?? can be written as ?? 0
+?? 1
?? +?? 2
2
2
where ?? =?? +?? .
3.2 Show that the set of matrices ?? ={[
?? -?? ?? ?? ]?? ,?? ??? } is a field under the usual
binary operations of matrix addition and matrix multiplication. What are the
additive and multiplicative identities and what is the inverse of [
?? -?? ?? ?? ] ? Consider
iiie map ?? :?? ??? defined by ?? (?? +???? )=[
?? -?? ?? ?? ]. Show that ?? is an isomorphism
(Here ?? is the set of real numbers and ?? is the set of complex numbers)?
(2013 : 10 Marks)
Solution:
Approach : Prove only the important parts in actual exam.
SCM?(2,?? ) where ?? (?? ,?? ) is the ring of 2×2 matrices with entries from ?? .
To show ?? is a field
and
[
?? -?? ?? ?? ]??? ?[
?? -?? ?? ?? ]
-1
=[
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]
-1
??? [
?? -?? ?? ?? ][
?? -?? ?? ?? ]
-1
=[
?? -?? ?? ?? ][
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]=[
???? +????
?? 2
+?? 2
-(???? -???? )
?? 2
+?? 2
???? -????
?? 2
+?? 2
???? +????
?? 2
+?? 2
]???
So, ?? is closed w.r.t. multiplication and has multiplicative inverse.
Also,
[
?? -?? ?? ?? ][
?? -?? ?? ?? ]=[
???? -???? -(???? +???? )
???? +???? ???? -????
]=[
?? -?? ?? ?? ][
?? -?? ?? ?? ]
i.e., multiplication is commutative.
That addition is commutative, closed and has inverse follows from ?? being subset of
?? (2,?? ) . ??? is a field.
Additive identity :
[
?? -?? ?? ?? ]+[
0 0
0 0
]=[
?? -?? ?? ?? ]=[
0 0
0 0
]+[
?? -?? ?? ?? ]
?[
0 0
0 0
]??? is additive identity.
Similarly, [
1 0
0 1
]=?? 2
is multiplicative identity.
[
1 -1
1 1
]
-1
=[
1
2
1
2
-1
2
1
2
]??? ?? (?? +???? )=[
?? -?? ?? ?? ]
To show ?? is isomorphism, ?? is linear.
?? (?? +???? )+(?? +???? )]?=?? (?? +?? +??(?? +?? )]
?=[
?? +?? -(?? +?? )
?? +?? ?? +?? ]=[
?? -?? ?? ?? ]+[
?? -?? ?? ?? ]
3.3 Show that ?? ?? is a field. Then find ([?? ]+[?? ])
-?? and (-[?? ])
-?? in ?? ?? .
(2014 : 15 Marks)
Solution:
?? 7
={[0],[1],[2],[3],[4],[5],[6]}
For ?? 7
to be a field, it should satisfy
(i) (?? 7
,+) is an abelian.
(ii) (?? 7
,?? ) is an abelian group, where ?? 7
*
=?? 7
-{0}
(iii) Distributive law.
(i) (?? 7
+)
+ [0] [1] [2] [3] [4] [5] [6]
Page 4
Edurev123
3. Fields
3.1 Consider the polynomial ring ?? [?? ]. Show ?? (?? )=?? ?? -?? is irreducible over ?? .
Let ?? be the ideal in ?? [?? ] generated by ?? (?? ) . Then show that ?? [?? ]/?? is a field and
that each element is of the form ?? ?? +?? ?? ?? +?? ?? ?? ?? with ?? ,?? ?? ,?? ?? in ?? and ?? =?? +?? .
(2010 : 15 Marks)
Solution:
Given :
?? (?? )=?? 3
-2
Let ?? (?? ),?? (?? )??? [?? ], and ?? (?? ) is reducible such that
?? (?? ) =?? (?? )·?? (?? )
Suppose, ?? (?? ) =?? +?? ? ?? (?? ) =?? 2
+?? ?? +?? ???? (?? ) =?? 3
-2=(?? +?? )(?? 2
+???? +?? )
? ?? 3
-2 =?? 3
+?? ?? 2
+???? +?? ?? 2
+???? +????
Comparing LHS & RHS, we get
?? +?? ?=0??? =-?? ???? +?? ?=0
??-?? 2
+?? ?=0??? =?? 2
???? ?=-2
???? 3
?=-2??? =-2
1/3
which is not a rational number
i.e., ?? ??? ??? ,?? ???
??? (?? ) is irreducible over ?? .
Now, ?? is ideal generated by ?? (?? )
i.e.,
?? =??? (?? )?
?
?? (?? )
?? is a field as ?? (?? ) is irreducible (theorem)
???
?? (?? )
?? =??? (?? )>+?? 0
+?? 1
?? +?? 2
?? 2
=?? +?? 0
+?? 1
?? +?? 2
?? 2
deg·(?? 0
+?? 1
?? +?? 2
?? 2
)<deg·(?? (?? ))
?????????????????????
remainder term
where ?? 0
,?? 1
,?? 2
??? . Now,
?? ?=?? +?? ?? 0
+?? 1
?? +?? 2
?? 2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )
2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )(?? +?? )
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? 2
+?? )
?=?? 0
+?? 1
?? +?? 2
?? 2
+?? which is equivalent to eqn. (1)
?
?? (?? )
?? can be written as ?? 0
+?? 1
?? +?? 2
2
2
where ?? =?? +?? .
3.2 Show that the set of matrices ?? ={[
?? -?? ?? ?? ]?? ,?? ??? } is a field under the usual
binary operations of matrix addition and matrix multiplication. What are the
additive and multiplicative identities and what is the inverse of [
?? -?? ?? ?? ] ? Consider
iiie map ?? :?? ??? defined by ?? (?? +???? )=[
?? -?? ?? ?? ]. Show that ?? is an isomorphism
(Here ?? is the set of real numbers and ?? is the set of complex numbers)?
(2013 : 10 Marks)
Solution:
Approach : Prove only the important parts in actual exam.
SCM?(2,?? ) where ?? (?? ,?? ) is the ring of 2×2 matrices with entries from ?? .
To show ?? is a field
and
[
?? -?? ?? ?? ]??? ?[
?? -?? ?? ?? ]
-1
=[
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]
-1
??? [
?? -?? ?? ?? ][
?? -?? ?? ?? ]
-1
=[
?? -?? ?? ?? ][
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]=[
???? +????
?? 2
+?? 2
-(???? -???? )
?? 2
+?? 2
???? -????
?? 2
+?? 2
???? +????
?? 2
+?? 2
]???
So, ?? is closed w.r.t. multiplication and has multiplicative inverse.
Also,
[
?? -?? ?? ?? ][
?? -?? ?? ?? ]=[
???? -???? -(???? +???? )
???? +???? ???? -????
]=[
?? -?? ?? ?? ][
?? -?? ?? ?? ]
i.e., multiplication is commutative.
That addition is commutative, closed and has inverse follows from ?? being subset of
?? (2,?? ) . ??? is a field.
Additive identity :
[
?? -?? ?? ?? ]+[
0 0
0 0
]=[
?? -?? ?? ?? ]=[
0 0
0 0
]+[
?? -?? ?? ?? ]
?[
0 0
0 0
]??? is additive identity.
Similarly, [
1 0
0 1
]=?? 2
is multiplicative identity.
[
1 -1
1 1
]
-1
=[
1
2
1
2
-1
2
1
2
]??? ?? (?? +???? )=[
?? -?? ?? ?? ]
To show ?? is isomorphism, ?? is linear.
?? (?? +???? )+(?? +???? )]?=?? (?? +?? +??(?? +?? )]
?=[
?? +?? -(?? +?? )
?? +?? ?? +?? ]=[
?? -?? ?? ?? ]+[
?? -?? ?? ?? ]
3.3 Show that ?? ?? is a field. Then find ([?? ]+[?? ])
-?? and (-[?? ])
-?? in ?? ?? .
(2014 : 15 Marks)
Solution:
?? 7
={[0],[1],[2],[3],[4],[5],[6]}
For ?? 7
to be a field, it should satisfy
(i) (?? 7
,+) is an abelian.
(ii) (?? 7
,?? ) is an abelian group, where ?? 7
*
=?? 7
-{0}
(iii) Distributive law.
(i) (?? 7
+)
+ [0] [1] [2] [3] [4] [5] [6]
[0] [0] [1] [2] [3] [4] [5] [6]
[1] [1] [2] [3] [4] [5] [6] [0]
[2] [2] [3] [4] [5] [6] [0] [1]
[3] [3] [4] [5] [6] [0] [1] [2]
[4] [4] [5] [6] [0] [1] [2] [3]
[5] [5] [6] [0] [1] [2] [3] [4]
[6] [6] [0] [1] [2] [3] [4] [5]
? All elements belong to ?? 7
- closure property.
? First row coincide with the top row, then [0] is identity element.
? [0] is in every row & column
? Inverse property satisfied.
([?? ]+[?? ]+[?? ]=[?? +?? ]+[?? ]=[?? +?? +?? ]=[?? ]+[?? +?? ]=[?? ]+([?? ]+[?? ])
? Associative property satisfied.
? Transpose of matrix equal to original matrix.
? Commutative property satisfy.
(ii) (?? 7
*
,?? )
? Every element belong to ?? 7
*
-closure property.
? Top row coincide with first row, Hence [1] is an identity element.
Page 5
Edurev123
3. Fields
3.1 Consider the polynomial ring ?? [?? ]. Show ?? (?? )=?? ?? -?? is irreducible over ?? .
Let ?? be the ideal in ?? [?? ] generated by ?? (?? ) . Then show that ?? [?? ]/?? is a field and
that each element is of the form ?? ?? +?? ?? ?? +?? ?? ?? ?? with ?? ,?? ?? ,?? ?? in ?? and ?? =?? +?? .
(2010 : 15 Marks)
Solution:
Given :
?? (?? )=?? 3
-2
Let ?? (?? ),?? (?? )??? [?? ], and ?? (?? ) is reducible such that
?? (?? ) =?? (?? )·?? (?? )
Suppose, ?? (?? ) =?? +?? ? ?? (?? ) =?? 2
+?? ?? +?? ???? (?? ) =?? 3
-2=(?? +?? )(?? 2
+???? +?? )
? ?? 3
-2 =?? 3
+?? ?? 2
+???? +?? ?? 2
+???? +????
Comparing LHS & RHS, we get
?? +?? ?=0??? =-?? ???? +?? ?=0
??-?? 2
+?? ?=0??? =?? 2
???? ?=-2
???? 3
?=-2??? =-2
1/3
which is not a rational number
i.e., ?? ??? ??? ,?? ???
??? (?? ) is irreducible over ?? .
Now, ?? is ideal generated by ?? (?? )
i.e.,
?? =??? (?? )?
?
?? (?? )
?? is a field as ?? (?? ) is irreducible (theorem)
???
?? (?? )
?? =??? (?? )>+?? 0
+?? 1
?? +?? 2
?? 2
=?? +?? 0
+?? 1
?? +?? 2
?? 2
deg·(?? 0
+?? 1
?? +?? 2
?? 2
)<deg·(?? (?? ))
?????????????????????
remainder term
where ?? 0
,?? 1
,?? 2
??? . Now,
?? ?=?? +?? ?? 0
+?? 1
?? +?? 2
?? 2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )
2
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? +?? )(?? +?? )
?=?? 0
+?? 1
(?? +?? )+?? 2
(?? 2
+?? )
?=?? 0
+?? 1
?? +?? 2
?? 2
+?? which is equivalent to eqn. (1)
?
?? (?? )
?? can be written as ?? 0
+?? 1
?? +?? 2
2
2
where ?? =?? +?? .
3.2 Show that the set of matrices ?? ={[
?? -?? ?? ?? ]?? ,?? ??? } is a field under the usual
binary operations of matrix addition and matrix multiplication. What are the
additive and multiplicative identities and what is the inverse of [
?? -?? ?? ?? ] ? Consider
iiie map ?? :?? ??? defined by ?? (?? +???? )=[
?? -?? ?? ?? ]. Show that ?? is an isomorphism
(Here ?? is the set of real numbers and ?? is the set of complex numbers)?
(2013 : 10 Marks)
Solution:
Approach : Prove only the important parts in actual exam.
SCM?(2,?? ) where ?? (?? ,?? ) is the ring of 2×2 matrices with entries from ?? .
To show ?? is a field
and
[
?? -?? ?? ?? ]??? ?[
?? -?? ?? ?? ]
-1
=[
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]
-1
??? [
?? -?? ?? ?? ][
?? -?? ?? ?? ]
-1
=[
?? -?? ?? ?? ][
?? ?? 2
+?? 2
?? ?? 2
+?? 2
-?? ?? 2
+?? 2
?? ?? 2
+?? 2
]=[
???? +????
?? 2
+?? 2
-(???? -???? )
?? 2
+?? 2
???? -????
?? 2
+?? 2
???? +????
?? 2
+?? 2
]???
So, ?? is closed w.r.t. multiplication and has multiplicative inverse.
Also,
[
?? -?? ?? ?? ][
?? -?? ?? ?? ]=[
???? -???? -(???? +???? )
???? +???? ???? -????
]=[
?? -?? ?? ?? ][
?? -?? ?? ?? ]
i.e., multiplication is commutative.
That addition is commutative, closed and has inverse follows from ?? being subset of
?? (2,?? ) . ??? is a field.
Additive identity :
[
?? -?? ?? ?? ]+[
0 0
0 0
]=[
?? -?? ?? ?? ]=[
0 0
0 0
]+[
?? -?? ?? ?? ]
?[
0 0
0 0
]??? is additive identity.
Similarly, [
1 0
0 1
]=?? 2
is multiplicative identity.
[
1 -1
1 1
]
-1
=[
1
2
1
2
-1
2
1
2
]??? ?? (?? +???? )=[
?? -?? ?? ?? ]
To show ?? is isomorphism, ?? is linear.
?? (?? +???? )+(?? +???? )]?=?? (?? +?? +??(?? +?? )]
?=[
?? +?? -(?? +?? )
?? +?? ?? +?? ]=[
?? -?? ?? ?? ]+[
?? -?? ?? ?? ]
3.3 Show that ?? ?? is a field. Then find ([?? ]+[?? ])
-?? and (-[?? ])
-?? in ?? ?? .
(2014 : 15 Marks)
Solution:
?? 7
={[0],[1],[2],[3],[4],[5],[6]}
For ?? 7
to be a field, it should satisfy
(i) (?? 7
,+) is an abelian.
(ii) (?? 7
,?? ) is an abelian group, where ?? 7
*
=?? 7
-{0}
(iii) Distributive law.
(i) (?? 7
+)
+ [0] [1] [2] [3] [4] [5] [6]
[0] [0] [1] [2] [3] [4] [5] [6]
[1] [1] [2] [3] [4] [5] [6] [0]
[2] [2] [3] [4] [5] [6] [0] [1]
[3] [3] [4] [5] [6] [0] [1] [2]
[4] [4] [5] [6] [0] [1] [2] [3]
[5] [5] [6] [0] [1] [2] [3] [4]
[6] [6] [0] [1] [2] [3] [4] [5]
? All elements belong to ?? 7
- closure property.
? First row coincide with the top row, then [0] is identity element.
? [0] is in every row & column
? Inverse property satisfied.
([?? ]+[?? ]+[?? ]=[?? +?? ]+[?? ]=[?? +?? +?? ]=[?? ]+[?? +?? ]=[?? ]+([?? ]+[?? ])
? Associative property satisfied.
? Transpose of matrix equal to original matrix.
? Commutative property satisfy.
(ii) (?? 7
*
,?? )
? Every element belong to ?? 7
*
-closure property.
? Top row coincide with first row, Hence [1] is an identity element.
? [1] is in every row & column.
? inverse property satisfied.
? ([?? ]×[?? ]×[?? ]=[(?? ×?? )×[?? ]=[?? ×?? ×?? ]=[?? ]×[?? ×?? ]=[?? ]×([?? ]×[?? ]) .
? Associative property satisfied.
? Transpose of matrix is equal to original matrix.
? Commutative property satisfy.
(iii) Distributivity :
[?? ]×([?? ]×[?? ])?=[?? ]×([?? +?? ])=[?? (?? +?? )]
?=[???? +???? ]=[???? ]+[???? ]=[?? ][?? ]+[?? ][?? ]
([?? ]+[?? ])×[?? ]?=[?? ][?? ]+[?? ][?? ]
Similarly
??????????????????????????????????([5]+[6])
-1
???????? ?=[4]
-1
=[2]
???????????????????????????????????(-[4])
-1
?????????=([3])
-1
=[5]
3.4 Show that the set {?? +???? :?? ?? =?? } , where ?? and ?? are real numbers, is a field
with respect to usual addition and multiplication.
(2014 : 15 Marks)
Solution:
Let ?????????????????????????????????????? ={(?? +???? );?? 3
=1;?? ,?? ?|?? }
(i) Let (?? ,+) be an algebraic structure.
?(?? +???? ),(?? +???? )??? .
(?? +???? )+(?? +???? )?=(?? +?? )+(?? +?? )?? ?=?? +???? -(?? +?? )?|??
? Closure property satisfy.
(ii) Let, (?? +???? ),(?? +???? ),(?? +???? )??? .
[(?? +???? )+(?? +???? )]?=((?? +?? )+(?? +?? )?? )+(?? +???? )
????????????????????????????????????????????????????????????????????????????=(?? +?? +?? )+(?? +?? +?? )w???????????????????????????(i)
(?? +?? +?? )?R
(?? +?? +?? )?|??
?? +???? )+[(?? +???? )+(?? +???? )]=(?? +???? )+[(?? +?? )+(?? +?? )?? ]
=(?? +?? +?? )+(?? +?? +?? )?? (???? )
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