Infinity: a concept or number?

[micromass]

Indeed, things like $[x,+\infty)$ only have real numbers has elements. So infinity is not a member of the set. Furthermore, the notation "$+\infty$" is nothing more than a notation. It is a notation for

$$[x,+\infty) = \{y\in \mathbb{R}~\vert~x\leq y\}$$

If you don't like the infinity, then other notations are

$$[x,\rightarrow )~\text{or}~\uparrow x$$

 

[Number Nine]

So you consider infinity to be a number?

...as part of what set? With what operations?

 

[Diffy]

I don't understand why people on this forum respond the way they do to questions like these.

People asking these types of questions have little to no mathematical training. Trying to explain something like the extended reals to them just confuses the matter doesn't it?

Can we just assume these people are talking about the Reals? Simply because they obviously haven't studied or heard of anything else? Can't we just assume the question is "Is infinity in the Real number system?"

This way when someone asks this question, we can simply say: NO.

I really hate these threads, that are posted so often. And even when linked to the FAQ, the OPs don't read it.

Can we lock this? There is no math in it.

 

[micromass]

Can we lock this? There is no math in it.

Agreed.