QUOTE(Elnendil @ Oct 7 2010, 03:46 PM)
Yep. If a|b, there has to be some integer q that, when multiplied by a, equals b.
I STILL DON'T KNOW WHAT YOU'RE SAYING
Are you explaining divisibility to me? I was clarifying that it's not something you have to prove, because it's basically the definition.
QUOTE(Elnendil @ Oct 7 2010, 03:46 PM)
I've been throwing some other concept around recently, has to do with using arithmetic to find square roots. This isn't a theorem, just a plausible observation:
q=lim(x->1+) sqrt(b)/x
When solving, it makes sense in a way that well, if x=1, then q=sqrt(b). But the observation is that you can get an approximation if q is an integer, when sqrt(b)/x and x approaches 1 from the right. Like how sqrt(33)=5.744... So there is some sqrt(x) that you can multiply into 5 that will equal sqrt(33) [5*sqrt(x)=sqrt(33)]. Then I divided both sides by sqrt(x), and I noticed that every time I pulled out a new decimal place, sqrt(x) approached 1 from the right, hence the observation. I showed this to the professor and he mentioned some other theorem...Newtons...gah, I forget the name. Its in my calculus book, i'll look into it later; has to deal with constantly finding approximations to find roots. I'll also say from observation that 1<=x<2 and q is the greatest integer of the root. Anyways, what do you think Rai?
wut
Uh, Newton's Method is to use the derivative to approximate the zeroes of a function. It applies to only functions satisfying certain properties on an open interval of values (i.e. every open interval for which the function has the right properties lets you use Newton's method on it). Off the top of my head: x_{i+1} = x_i - f(x_i)/f'(x_i). In other words, there's a sequence x_0, x_1, x_2, ... that converges to x where f(x) = 0. I still have no idea what you're talking about. Yes, when you divide a real number by a smaller integer, you get closer to 1. What?
If you want to solve 5*sqrt(x) = sqrt(33), then x = 33/25. I... don't think that's what you're saying...
Uh... Define [x] as the greatest integer less than or equal to x (floor function). In other words, [x] is an integer such that [x]<= x < [x]+1. Then are you saying that 1 <= x / [x] < 2? Yes, that's true, for x >= 1. The first inequality is true by virtue of x >= [x] by definition, therefore x/[x] >= [x]/[x] = 1. Assume the second is false. Then x/[x] >=2. Then x >= 2*[x] = [x] + [x]. But since x >= 1, [x] >= 1. So x >= [x] + [x] >= [x] + 1, which contradicts the definition of [x]. Is that what you want?
QUOTE(Elnendil @ Oct 7 2010, 08:23 PM)
I should probably stop talking so much about math before this becomes Math General though, so I guess i'll keep it to PM from now on. Soon i'll be able to just do most of these problems with relative ease, can't wait.
I don't think I can be PM'd. I'm banned.