Question 974043
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            The answer by  @CubeyThePenguin  is   TOTALLY   and   ABSOLUTELY     W R O N G  (!)




For the sum   (a + b),  the counter-example is    a = {{{1 + sqrt(2)}}},    b= {{{1 - sqrt(2)}}}.



For the product    {{{a*b}}},    the counter-example is    a = b = {{{sqrt(2)}}}.



For the ratio    {{{a/b}}},    the counter-example is  the same    a = b = {{{sqrt(2)}}}.



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