Of course ^^

It depends... Is "x divides 2" appropriate for you ?1. I've never encountered the symbol "|", as in (x | 2) . What does it mean, and how would I go about deciding it's use?

Yes, sort of. Imagine f(x) represents the y-ordinate of any point. If you increase k, it means you increase f(x), that is to say for each point, you increase the y-ordinate. So it looks like you're stretching (or narrowing if you make k decrease) the curve.2. What role does 'K' play in the equation f(x) = k(x - s)(x - t)(x - u)etc.?

I know that if k is negative, we reflect the graph in the x-axis, but is it also (as I remember it) the term that will stretch the graph vertically?

Yes it is. You're told that this equation holds for 0<x<4. Thus it can be considered as the domain.3. An application question gives me a function , 0 < x < 4 and asks me to state the restricted domain... I'm not sure if it *is* 0 < x < 4, or what. It's just a guess, and I need an explanation really.

If you want an example of an application... hmmm let's see.

You can define a function as being :

It means it takes these values if x is in the given domains.

In that case, the restricted domain of -170.56x^2 + 249.62x + 1257.80 is (0;4)

I hope it looks clear... If not, just ask.