This was a challange question and I am not sure how to do this.. help would be appreciated thxhttp://img17.imageshack.us/img17/5006/83668755.jpg

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- March 17th 2009, 09:53 AMrajrRing and Groups
This was a challange question and I am not sure how to do this.. help would be appreciated thxhttp://img17.imageshack.us/img17/5006/83668755.jpg

- March 17th 2009, 10:39 AMstapel

Subtract from either side. See if that leads anywhere helpful...?

...where is the group's identity element. The result follows immediately. (Wink) - March 17th 2009, 10:48 AMrajr
thx for the reply and I can understand the second part and for the first part if I takeaway a+b from both sides then I will get ab = -ba but is it ok to say that it is commutative just from that step or do I have to go further any more steps to prove it

I think for the part (ii) I have to do like as follows:

b(a+a) = 0;

therefore a+a =0 is it right

thx once again for ur help(Happy)