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Type I -- Logarithm Bases


jesli

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With limitations, the negative values, for log(a)c=x

log(-2)-8=3 mathematically this is correct because (-2)^3 is 8. But when you are dealing with what you are in your project it doesnt.

(-2)3 = (-2)*(-2)*(-2) = -8. =)

few questions...

I did that, but my teacher says we have to explain why graphing it can justify.. like, I see a pattern, but I have no idea how to explain how what I'm looking at helps justify the pattern.

Well yeah, you should be able to explain why it only works after a certain number. However, I can't tell you what the reason is. It shouldn't be too difficult when you really look at it. Still, it's better to have a graph with the correct domain and no explanation, than no graph at all. This is because criterion X (I forget which one..) says that for the top mark, you need to have the correct limitation, but it does not state that you need to prove how you found it. That's more of a criterion B (communication) issue.

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  • 2 weeks later...

i'm working on doing my final write-up for this portfolio '(I'm supposed to turn it in tomorrow) and i just realized that I never did justify my answers using technology. I know i could convert all the logs to base 10 or make an excel tables of all the p/q values (i'm on the right track, right?), but i'm not sure how doing either of those things would "justify" my answers. Could someone please help me understand this? Also, are there any other methods of using technology that would be useful in this situation? Thanks so much in advance for any help you can give me!

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I'm not sure about what the portfolio asks, does it ask explicitly for proof using technology? If it is just to get marks on the technology criterion, then an excel table is fine. Technology is supposed to help you, and also allow you to see that while it is useful, there are limitations.

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It says, "Find an expression for the nth term of each sequence. write your expressions in the form p/q where p, q E Z. Justify your answers using technology." so it sounds to me like you don't have to find your answers using technology, just verify that they are correct in some way. So you think an excel table of the p/q values i found would somehow fulfill that requirement?

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I know, I don't really see how graphing would help justify our answers. I ended up making an Excel table for each sequence and spouting some BS about how my "logical method" of finding the expressions was "confirmed mathematically" by the formulas in Excel. Phooey. well, it kind of sounds legit, even if it turns out not to be. Well, good luck with your portfolio, Faerie!

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okay, i am sooooooooo confused on this portfolio right now.

in number 2, where they say "Find an expression for the nth term of each sequence. Write your expressions in the form p/q, where p,q Є Z"

what does that symbol before z mean?

do they want an expression, as in, p^(0+1)/q, like a formula to find any term?

i know the bases in the sequences in #1 are going up by exponents of 1, because in the first term, it's 2, and in the second, 4, which is 2 squared.

but how do i put that in a fractional form? gahhhhhh so bewildered.

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Z means integers. Click on the link if you don't know what integers are, it's very simple. It won't be p^x, but rather something like p*x/q, p/x/q, p+x/q, p-x/q. The change might also take place in q instead of p! I won't tell you which one, you'll have to find out for yourself.

When you solve the examples, finding the fractional form will be clear enough.

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hello everyone,

it says that you need to test the validity of your general statement using other values of a,b and x

does this mean that you make up other examples, or do you use the ones that they have already given you?

and you guys said that log(ab)x =???.. how did you come up with that?

thank you! =)

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Use your own examples to show the validity.

We cannot tell you how to find the general statement, this is the only remotely difficult task in the IA and it constitutes malpractice to use someone else's work for this part.

In fact, I'll remove the general statement from your post and previous posts now.

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First off, thanks a lot guys, this thread has really helped me get on the right track with this portfolio.

Now, I'm currently on the part where I find the general statement. I think I know what it is, and I know how to prove it using logarithm laws, but I'm a little confused by the prompts.

It tells me to find the general statement. Fine, I can do that, but then at the very END of the portfolio it asks me to explain how I arrived at it. When I first say the general statement should I just cite the fairly obvious pattern and leave the logarithm laws for later? If I just proved it with logarithm laws now would that count as answering that final prompt?

Sorry if the answer is obvious, I just don't want to lose marks for a stupid reason =)

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First off, thanks a lot guys, this thread has really helped me get on the right track with this portfolio.

Now, I'm currently on the part where I find the general statement. I think I know what it is, and I know how to prove it using logarithm laws, but I'm a little confused by the prompts.

It tells me to find the general statement. Fine, I can do that, but then at the very END of the portfolio it asks me to explain how I arrived at it. When I first say the general statement should I just cite the fairly obvious pattern and leave the logarithm laws for later? If I just proved it with logarithm laws now would that count as answering that final prompt?

Sorry if the answer is obvious, I just don't want to lose marks for a stupid reason =)

I have the same problem. I try to prove it i state the statment, but then i would lose marks.

I also have trouble with the "discuss the scope and/or limitations of a, b, and x."

I don't quite understand what they mean by the scope. I get how in logabx, x cannot equal zero, and the demoninator cannot equal zero, but what about the scope?

Edited by IB:Spartan
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Scope: does it work from negative infinity to infinity? If not, what is the scope?

About the general statement: You can both

a) first find the general statement deductively (i.e. by examples) and later solve it algebraically when it asks you how you arrived to it.

b) find the general statement algebraically and thus solve the problems. There is no need to restate the solution, but it is a good idea to state something along the lines "Using algebra, we will show the general statement is found as follows:" to make sure that your teacher will know that this is you proving how you found the general statement. I did this and I got full marks for the criterion.

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Wanderer:

Excuse me?

1)You procarastinated a project that should have taken 10 days at least of your time.

2)We do NOT send or share portfolios because that is against IB Regulations.

3)We're not going to help you unless you make an attempt.

4)Do not urge people to help you in that way.

5)Don't text speak.(I know Joel :) , it came in context).

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Wanderer:

Excuse me?

1)You procarastinated a project that should have taken 10 days at least of your time.

2)We do NOT send or share portfolios because that is against IB Regulations.

3)We're not going to help you unless you make an attempt.

4)Do not urge people to help you in that way.

5)Don't text speak.(I know Joel :( , it came in context).

Hey don't get all mad at me...

i finished working out the portfolio i just do not know what format to write it down in..

my teacher says it should be a continuous piece of work.. i just don't know how to do that..

i have a rough draft ready but as i have never done a portfolio before in my life i have no idea how is it supposed to be like..

i was just wondering if you guys could help me with that.. thus i wanted to view someone else's portfolio to get a hang of how i am supposed to write it down..

besides i want to know which graph software to use for my portfolio...

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It doesn't take much reading to find what graph software people have used. Try Graphical Analysis 3.4.

We're all in the same situation where we don't know what a portfolio looks like, but we all have to figure it out for ourselves. It's tough, but that's IB.

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