Yahoo Answers: Answers and Comments for Pliz help me, I have Set theory, Relations and Groups Problems? [Mathematics]
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From alberto m
enUS
Fri, 20 Jun 2008 23:34:46 +0000
3
Yahoo Answers: Answers and Comments for Pliz help me, I have Set theory, Relations and Groups Problems? [Mathematics]
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https://answers.yahoo.com/question/index?qid=20080620233446AAXLMHb
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From Alam Ko Iyan: i will help you with some.. . .
2 .. . . x*...
https://answers.yahoo.com/question/index?qid=20080620233446AAXLMHb
https://answers.yahoo.com/question/index?qid=20080620233446AAXLMHb
Sat, 21 Jun 2008 03:36:11 +0000
i will help you with some.. . .
2 .. . . x*y = xy + 1
while y*x = yx + 1 = xy + 1 ... thus the relation is commutative
now, consider (1 * (2 * 3)) = 1 * 7 = 8
then ((1 * 2) * 3) = (3 * 3) = 10
thus it is not associative.
3. θ^(1) = (x  b) / a ... thus it is necessary that a ≠ 0
5. supposing n is odd, then n = (2k+1) for some integer k
then n^2 = 4k^2 + 4k + 1 = odd
thus we contradict the hypothesis.
thus if n is odd, then n^2 is odd... by contrapositivity
if n^2 is even, then n is even. (it also needs law of excluded middle, n is not odd means n is even)
.. . .. .