Algebra Flashcards

1
Q

Relatie reflexiva

A

x r x

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2
Q

Relatie tranzitiva

A

Daca xry si yrz => xrz

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3
Q

Relatie simetrica

A

xry => yrx

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4
Q

Relatie antisimetrica

A

Daca xry si yrx => x = y

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5
Q

Relatie totala

A

Avem xry sau yrx

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6
Q

Relatie de echivalenta

A

Daca e reflexiva, tranzitiva si simetrica

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7
Q

Relatie de preordine

A

Daca e reflexiva si tranzitiva

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8
Q

Relatie de ordine

A

Daca e reflexiva, antisimetrica, tranzitiva

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9
Q

f injectiva

A

f(x) = f(y) => x = y
x != y => f(x) != f(y)

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10
Q

f surjectiva

A

f(x) = y

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11
Q

f bijectiva

A

Daca este injectiva si surjectiva

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12
Q

f inversabila

A

Daca f injectiva => f inversabila

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13
Q

Legea este asociativa daca:

A

(xy)z = x(yz) (* “compus cu”)

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14
Q

Legea este comutativa daca:

A

xy = yx (* “compus cu”)

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15
Q

Legea admite element neutru “e”

A

Daca xe = ex (* “compus cu”)

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16
Q

Element “x” este simetrizabil pe o lege daca:

A

xx’ = x’x = e (* “compus cu”)

17
Q

Partea stabila a lui “A”

A

H⊂A (H este partea stabila a lui A)
daca ∀x,y∈H, x*y∈H

18
Q

M(A,*) este “semigrup” daca:

A

Legea este asociativa

19
Q

M(A,*) este “semigrup comutativ” daca:

A

Legea este asociativa SI comutativa

20
Q

M(A,*) este “monoid” daca:

A

Legea este asociativa SI admite element neutru

21
Q

M(A,*) este “monoid comutativ” daca:

A

Legea este asociativa SI admite element neutru SI comutativa

22
Q

M(A,*) este “submonoid” daca:

A
  1. H este partea stabila a lui A (pentru x,y∈H, x*y∈H)
  2. e∈H
23
Q

Multimea elementelor inversabile

A

xx’ = x’x = 1

24
Q

Cand este un Monoid, “Grup”?

A

Cand orice element este simetrizabil

25
Q

Morfisme de Grupuri (cand sunt?)

A

f(x.y)=f(x).f(y)

26
Q

Cum se numeste un “morfism bijectiv”?

A

Izomorfism

27
Q

Cum se noteaza 2 grupuri G1, G2 izomorfisme? (care este simbolul)

A

~= (squigly line + equal sign)

28
Q

Daca G1=G2 => f:G->G, cum se numeste G?

A

G endomorfism

29
Q

Daca f:G->G este izomorfist cum se numeste f?

A

f automorfism

30
Q

Cum se noteaza un Subgrup?

A

<= (ex: H <= a lui G)