Umm... I meant multiply?

Yeah, it's clearer if you use *. In further math, you get variable introduced, and using x looks like one.

I also like to use spaces between values and operators, but that's partly just preference.

Especially when you said "year 8 math". Not sure about U.S., but in Canada, algebra = grade 8

Well probably ^
But bare in mind we've only just started year 8. We started 7th September.

Poland: year 7=algebra, so if that's the case, just starting 8th (as I am) is no excuse.

That's hardly fair. Different countries have different curriculum. Different school's have different curriculum. My brothers' school taught them stuff in yr 7 that I wasn't taught then.

of course, but then, I was referring more to it not being much of an excuse here.

We did stuff like 3x + 4x = 7x and how x was more like two c's

They're saying to use * instead of x when typing, though because it gets confusing. I usually just use brackets rather than a multiplication sign, anyway.

Brackets can be misleading: to some of us, they suggest vectors.

I assume Liv meant parenthesis.

(8)(5)=40

That crossed my mind too. Implied multiplication with parentheses can be misleading too, though: is f(x) "f times x" or "f of x"?

The result of all this is that there's no single absolutely unambiguous way to express multiplication. It seems to me that the most widely understood ways are * and parentheses, with care taken to avoid the ambiguous circumstances surrounding each.

If f is known to be a function and not a number, then f(x) = fx.

Edit: By that I mean, a function is never really multiplied by a number, but a similar notation for multiplication is valid for applying functions to elements of a set.

So, in my calc book there's a notation of a function written as:

Except imagine that the square brackets are one big curly bracket. What does this notation mean? I skipped precalc, so I assume this is one of those things I missed out on.

For all values that are not X = 2, y = 4 - x. For value of X = 2, y = 0. Basically it's a y = 4 - X graph with an exception at value X = 2.

Example.
f(x) =
[-1 if x < 0 ]
[15 if x = 0 ]
[ 1 if x > 0 ]

Basically this says from the interval (-∞,0) the y value is -1. At x = 0 the y value is 15. From the interval (0,∞) the y value is 1.

2+2=4

Don't spam, talon.

Thanks, Atrophy. 'Nother question.

So, the text book I'm using vaguely teaches us that any point can have a limit (except the certain specific exceptions), and that's all fine and dandy, until it asks us to fine all the limits on a graph, and there are no existing, er, hole-based limits (by hole, I mean the point where a function can't exist) on the graphs, Ought I just put "No Limits"? Or should I list the limits that don't exist and say every other point has a limit? Or can real points even have limits? My calc teacher's been gone the past days, and the sub hasn't got a clue.

Related: Say you have one of the cases where a limit can't exist, such as on a vertical asymptote, and part of the problem states that that point has a value. Does that value become the limit, even though it wouldn't exist normally?

Semi-Related: My calc teacher was (when he was here) teaching the class by teaching us how to use a TI-89. Problem is, I don't have a TI-89.

On any two variable function graph there are an infinite number of points and therefore an infinite number of limits(I think, I can't think of any functions that aren't continuous on SOME interval). Remember a limit is the value that the function approaches, not it's actual value there.

To answer your question I would put the intervals where the limits do exist.
Graph y = sin(π/x). In the domain (-1,1) the y-values fluctuate an infinite number of times, yielding an undefined limit for any number in that domain. I'd answer this problem with "Limits exist for all numbers on intervals (-∞,1) and (1,∞)

To answer your related question, No. Graph y = 1/x. The limit as x approaches 0 is ∞, that will remain the limit regardless of if there is a provision stating that at x = 0, y = 3.

TI-89...eww. TI-83 Plus here, tried and true.

To be precise, the limit is ∞ only approaching from the right. The limit from the left is -∞.

Serious lapse in brain power here: can anyone help me find a function for linearly mapping the interval (a, b) to (c, d)?

So you want a line going between those two points?

Can someone please explain integers to me? My math teacher doesn't quite relate well to people my age.

Basically, integers are numbers that you can write without a decimal point. -5, 0, and 200182391 are all integers. 4/3, 0.5, and 3.14159... are not.