Also prove.
1. let a,b be elements of Z. Prove if a^2 + 2b^2 is congruent to 0(modn), then either a and b are both congruent to 0 module 3 or neither is congurent to 0 modulo 3.
2. let a,b,c,d be element of Z. prove: for a|b if is necessary that a|(a+b)^2.
3. let a,b,c,d be element of Z. prove: if a is congruent to b(modn) and a is congurent to c(modn), then a is congurent to (2b-c)(modn).
4. definition: for a real number x, |x| = {x if x>= 0, -x if x < 0}. prove: for every a,b, element of R, |a+b|<=|a|+|b|.
2006-10-08
18:19:46
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1 answers
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asked by
st234
2
in
Mathematics