#math - Fri 27 Apr 2007 between 03:27 and 04:06



rook2pawn(because a nonsurjective f, could still have f(1) -> 1)
TRWBWrook2pawn: yes, yes, ?
rook2pawnand so we could say f(n*1_R) = f(0_R) = 0_S = f(1_R + 1_R + ... + 1_R) = nf(1_R) = n*1_S -> hence characteristic can get preserved between nonsurjective maps
TRWBWrook2pawnk: homorphism implies f(0_R)=f(0_S), so if R has characteristic n, then S must have characteristic m|n. for example the homorphism from Z_(ab)->Z_a given by f(x)=b*x
rook2pawn: oops my mistake
rook2pawn: i was going group there for a second
rook2pawn: for example homorphism from Z_(ab)->Z_a given by f(x)=x mod a.
rook2pawn: make sense? Z_ab has characteristic ab, Z_a has characteristic a, a|ab
rook2pawnOh okay so it simply happents that n*1_S = 0_S where n is the characteristic from R but n is not necessarily the smallest positive integer that does the job
TRWBWrook2pawn: i'm assuming here both rings have units and f(1_R)=1_S and characteristic is the smallest n>0 s.t. n*1=0
keoki_zeequick question to ALL: how does one prove the uniqueness of the multiplicative identity in a ring?
rook2pawnlet f be the fake identity , 1 the real one. 1 * f = 1, but 1*f = f as well hence f = 1
mrgibsonSimple question, I have an apple at a base price of 1$, but for each extra apples I bought the price increase by 10%, If I want for example 20 apples, I can start counting every prices one by one, but I guess a formula can be used ?
sumptmrgibson: if I am not mistaken you can use a geometric series
er an arithmetic series
ddarkwhat the fuck is the deal with imaginary numbers
kestas% Integrate[e^(-1/(x^2+x)),x]
mbotkestas: Integrate[e^(-(x + x^2)^(-1)), x]
boumaddark: whats the solution to x^2 +1 =0
ddarki
bouma, it is equal to i
boumaim just starting to learn about where it comes from more formally in a ring theory subject
kestas% Integrate[e^(-(x + x^2)^(-1)), x]
boumainteresting stuff
mbotkestas: Integrate[e^(-(x + x^2)^(-1)), x]
kestasyoure not even trying
ddarkbouma, yeah I'm taking intermidiate algebra right now it sure as hell is more interesting than doing polynomials for an entire semester.
boumabasically x^2 +1 , is irreducible, in a similar way to primes being irreducible
this leads to alsorts of wonderful things, but its not just pulled from somewhere... although it seems that way until, say, 3rd uni doing pure math.. its a long haul, but if you want to know all the info is avail more readily (books, interweb.. etc)
mrgibson_I just asked a question about apples, someone seen it?
kestas% Integrate[(-1)/(x + x^2), x]
mbotkestas: -Log[x] + Log[1 + x]
Ultra5pamhey
what is difference between -1 and -1.0?????
mrgibson_one is unsigned integer and the other is a float?
erm signed
JabberWalkieUltra5pam 1-(-1.0)=0
Ultra5pamright.
is it 0 or 0.0?
JabberWalkie0....0.0 would be kind of redundant...

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