TUGAS OPERASI BINER MATIF
2. Tunjukan bahwa himpunan bilangan kelipatan 2 merupakan grup
terhadap a*b=a+b
b. Tentukan apakah berupa group,monoid, atau semigroup.
a. a * b =
a + b + 3
b. a
* b = a + b - 2ab
3. misalkan G= {-1,1}
tunjukan bahwa G adalah group abel dibawah perkalian
biasa
a*b = a+b
4. diketahui himp R=bilangan real tanpa -1
a+b =ab+a+b
tentukan sifat operasibinernya
jawab
2. a
* b = a + b
·
Tertutup
bila :
a = 1 maka : a
* b = a + b
b
= 3 a * b =
1 + 3 = 4
·
Asosiatif
(a * b)
* c = a *
(b * c)
(a * b)
* c = (a + b)*c (a *
b) * c =
a * (b + c)
= a+b+c =
a + b + c
·
Invers
a -1=a -1* a =e
a* b= a+b misalkan a -1 = b
a*b= a+b=0
=a + (-a) =0
0=0
a*b= a+b=0
=a + (-a) =0
0=0
·
Komutatif
a * b = b
* a
a + b = b + a
Maka a * b = a + b anggota bilangan kelipatan 2
merupakan group abel
a. a
* b = a + b + 3
·
Asosiatif
(a *
b) * c
= a *
(b * c)
(a *
b) * c = (a
+ b + 3) * c (a
* b) * c = a *
(b + c + 3)
= n
* c
= a * n
=
n + c + 3 = a +
n + 3
=
a + b + c + 6 = a + b + c +
6
·
Identitas
a * e =
e *
a = a
a * e =
a
a * b =
a + b + 3 e * a e + a + 3 = a + e + 3
a * e =
a + e + 3
a = a
a = a + e
e = -3
·
Invers
a -1 = a -1* a = e
a * b =
a + b + 3 Misalkan : a -1 = b
b = - a - 3
a * b =
a + b +3 = -3
=
a + (-a - 3) + 3 = -3
0 ≠ -3
·
Komutatif (abel)
a * b =
b *
a
a
+ b + 3 = b + a + 3
Maka
a *
b = a + b + 3 merupakan monoid abel
b. a
* b = a + b - 2ab
·
Asosiatif
(a *
b) * c
= a *
(b * c)
(a *
b) * c = (a
+ b – 2ab) * c (a *
b) * c =
a * (b + c – 2 bc)
= n
* c
= a * n
= n + c - 2nc
= a + n – 2an
=
(a + b – 2ab) + c – 2(a + b – 2ab)c
= a + (b + c - 2bc) – 2a(b + c – 2bc)
=
a + b + c – 2ab – 2ac – 2bc + 4abc
= a + b + c – 2bc – 2ab – 2ac + 4abc
·
Identitas
a * e =
e *
a = a
a * e =
a
a * b =
a + b – 2ae
e * a =
e + a – 2ae = a + e – 2ae
a * e =
a + e – 2ae
– 4ae + a= a – 4ae
a = a + e – 2ae
e = -2ae
·
Invers
a -1 =a -1 * a =
e
a * b =
a + b – 2ae Misalkan : a -1 = b
b = - a + 2ae
a * b =
a + b = -2ae
= a + (-a + 2ae) = -2ae
2ae ≠ -2ae
·
Komutatif (abel)
a
* b = b * a
a + b – 2ab = b + a –
2ba
maka
persamaan a * b = a + b - 2ab disebut semigroup abel
3. a
+ b = a * b dengan G { -1, 1}
·
Tertutup
a + b =
a * b
= -1 * 1
= -1
·
Asosiatif
(a +
b) + c
= a +
(b + c)
(a +
b) + c = (a
* b) + c (a +
b) + c =
a + (b * c)
= n
+ c =
a +
n
=
(a * b) * c = a *
(b *c)
·
Identitas
a + e =
e +
a = a
a + e =
a
a + b =
a * b
e + a
e * a = a * e
a + e =
a * e
0 = 0
a = a * e
e = 0
·
Invers
a -1 = a -1 + a = e
a + b =
a * b Misalkan : a -1 = b
b = 1/a
a + b =
a * b = 0
= a * (1/a )
= 0
1 ≠
0
·
Komutatif
a
+ b = b + a
a * b =
b * amaka fungsi a + b = a * b dengan G { -1, 1} bukan merupakan
Group melainkan semigroup abel
4.
a + b = ab + a + b dengan R = bilangan real
·
Tertutup
a + b =
ab + a + b a + b =
(3*2) + 1 + 2
a
= 3 = 9
b
= 2
·
Asosiatif
(a +
b) + c
= a +
(b + c)
(a +
b) + c =
(ab + a + b) + c
=
n +
c
= nc + n + c
= (ab + a + b)c + (ab + a + b) + c
=
abc + ac + bc + ab + a + b + c
(a
+ b) +
c = a + (bc + b + c)
= a
+ n
= an + a + n
= a(bc + b + c) + a + (bc + b + c)
= abc + ac + bc + ab + a + b + c
·
Identitas
a + e =
e +
a = a
a + e =
a
a + b =
ab + a + b
e + a
ae + a + e = ae + a + e
a + e =
ae + a + e
a2e + a + e = a2e + a + e
a
= ae + a + e
e
= ae
·
Invers
a -1= a -1 + a =
e
a + b =
ab + a + b Misalkan
: a -1 = b
ab
+ b = -a
·
Komutatif a + b =
b +
a
ab
+ a + b = ba + b + a
maka fungsi a + b =
ab + a + b dengan P bilangan real merupakan semigroup abel
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