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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 299

Hi, : http://imageshack.us/photo/my-images/827/34f2.png/

I'm just wondering, I know that a rational expression can't be divided by 0, but what does he man by "identically" ???I feel like there's something I'm missing... any help please ! Thank you !

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,891

x-x is identically equal to 0 because it is 0 for any value of x.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,791

hi Al-Allo

In your example you could drop the word altogether and have "The only restriction is that the divisor must not be equal to zero" and it still makes perfect sense. I've been trying to find situations where just using 'equals' is not appropriate ... without much success I have to say.

Some mathematicians use 'identically equal' instead of 'equivalent' and it is often used for identities eg.

and also eg.

If you google the two word phrase you'll get more examples.

Meanwhile, here's a challenge for members:

Find an example where you cannot leave out the word 'identically' without changing the meaning.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**Al-Allo****Member**- Registered: 2012-08-23
- Posts: 299

Ok, thank you.

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,891

Hi Bob

In math or in general?

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,791

hi Stefy,

I'm be interested in either / both.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,891

In math such an example, I think, doesn't exist. But, either way, the question is a bit ambiguous.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,791

I suppose what I'm really saying is the word 'identically' is redundant in the sentence. So then I wonder, is it always redundant. So far, I think, yes. So I'm curious about whether a case exists where it isn't.

I prefer concepts to words in maths. There are often many ways of expressing the same idea. Sometimes posters get hung up on the words when I think they should be concentrating on the concepts. The same is true of the symbols used. eg. the recent Boolean algebra question. There are at least three different notations there, but the underlying maths is consistent throughout.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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