6-1 INTEGERS AND OPERATIONS ON INTEGERS MATH 210 The
... a+b = b+a still true. To prove it, we have to review all the cases. (a+b)+c = a+(b+c) likewise (& there are more cases to consider). 0 still works, for ALL elements b å Z For each a å Z, there is a unique c å Z such that a + c = 0 and c + a = 0. [see above!] ...
... a+b = b+a still true. To prove it, we have to review all the cases. (a+b)+c = a+(b+c) likewise (& there are more cases to consider). 0 still works, for ALL elements b å Z For each a å Z, there is a unique c å Z such that a + c = 0 and c + a = 0. [see above!] ...
