Indre Posted June 13, 2011 Report Share Posted June 13, 2011 I need help with all the questions.. im really bad at maths..!! you can't solve it for me, but at least guide me? Please help me with the general statement (q.2), I still dont get it, even after having read all the posts..I'm not sure I'm right, but the graph you had to plot in q2 is the graph of the exponential function. All that's left is only to calculate the vlue of the exponent! Reply Link to post Share on other sites More sharing options...
dessskris Posted June 14, 2011 Report Share Posted June 14, 2011 well sorry :/I have posted all guidance I could give last time...unless you have other questions.if you don't understand, close all your other browser tabs and put aside all other things that can distract you. now focus on this IA only. read the past posts carefully!! don't just skim through them once or twice.if you still don't understand, get a tutor and ask them. or you can ask us to make it clear. but specify which one! we can't re-explain everything...and I know of people who read this whole thread and actually understood and did well on their IAs. they PMed me. so I'm sure I've written clearly enough and it's quite straightforward. otherwise they wouldn't have understood...and no it's not exponential :/ it's much simpler than that! it's quadratic... Reply Link to post Share on other sites More sharing options...
two1frets Posted June 14, 2011 Report Share Posted June 14, 2011 bahhhh! you guys saved me! i was getting so frusterated with doing this stuff in the beginning i was doing the sum of an arithmetic sequence (which actually works!) but is so damn complicated i got my stuff all together and now ive got the GS and it feels amazing! now time to write this baby up and im all set thanks again guys, really appreciate all the help! Reply Link to post Share on other sites More sharing options...
eleonore Posted June 19, 2011 Report Share Posted June 19, 2011 Hello everybody, I was given a math portfolio on lascap's fraction/triangle. I found the formula for the numerator but i am having problems with finding it for the denominator. Mainly there is this series of fractions. 1 1 1 3/2 1 1 6/4 6/4 1 1 10/7 10/6 10/7 1 1 15/11 15/9 15/9 15/11 1 and the portfolio asks me to find the numerator formula (which i did). 0.5X^2+0.5X . which is the same as X(X+1)/2 <----triangular numbers formula. As i said before the problem lies on the denominator formula finding. I swear i tried so hard to find it but it was no use, i am at a dead end, and if i don't find it i can't go on with the following questions... I tried with parabola functions too, but i couldn't find a proper pattern. Am i missing something? do you guys know how to get to the formula? Thank you in advance If you want some of the questions from the portfolio here they are.: Find the sixth and Seventh row. Describe any patterns you used. Let E n ® be the (r+1)th element in the nth row, starting with r=0 Example: E 5 (2) = 15/9 Find the general formula for En® Test the validity of the general statement. Discuss the scope and/or limitation of the general statement. Explain how you arrived to the general stament Any clues towards the general statement would be really appreciated as well as any help at all. Reply Link to post Share on other sites More sharing options...
dessskris Posted June 19, 2011 Report Share Posted June 19, 2011 read through this whole thread: http://www.ibsurvival.com/topic/14107-type-i-lacsaps-fractions/I believe the answer can be found there. if not please post your inquiries there. Reply Link to post Share on other sites More sharing options...
sofija3737 Posted June 19, 2011 Report Share Posted June 19, 2011 hwy everyone, I have huge trouble too. well, I've noticed that every denominator is a sum of previous row number and previous denominator but I cannot figure out the En(3) sequence and also I cannot put it into a general statement. Any ideas? Reply Link to post Share on other sites More sharing options...
dessskris Posted June 19, 2011 Report Share Posted June 19, 2011 read http://www.ibsurvival.com/topic/14107-type-i-lacsaps-fractions/page__view__findpost__p__109760 and http://www.ibsurvival.com/topic/14107-type-i-lacsaps-fractions/page__view__findpost__p__109764or actually just read the whole thread... there aren't too many posts.if some parts are still not clear just ask again. Reply Link to post Share on other sites More sharing options...
Shyamal Vibhakar Posted June 20, 2011 Report Share Posted June 20, 2011 Yeah, I get you. It's just gonna be hard for me to explain it in words. But if I am getting you, then after the row with "15/11" would be 1 21/16 21/13 21/? 21/13 21/16 1 right? What could be the middle number?? Yes, you're correct! the middle number would be 21/11 as in the previous 2 rows the difference of the third term was of 2. Therefore the difference between the third term between row 6 and row 5 should be of 3 as they are in sequence as discussed above! I hope you get it! Reply Link to post Share on other sites More sharing options...
Shyamal Vibhakar Posted June 20, 2011 Report Share Posted June 20, 2011 mmm are you sure it's correct? I've just tried to work out the general statement of En(r ) and I got a quite complicated formula in terms of n and r. it did require some effort to get to the general statement. there are many ways to get to the GS but I myself used the graphical method (b/c I'm lazy...) but if you know how to find it using another method, go for it. I personally don't favour the graphical method (plotting a graph and finding the best fit curve) for a Math IA, though it's a use of technology The numerator part is very obvious and easy, right? So I don't need to discuss it. After you found the 6th and 7th rows, draw a new triangle if possible so you can see the patterns more easily. Remember that 1 is the 1st term in each row, and in this term r=0. When r=1 (the 2nd term from the left), get a table of the denominators and the n (n starts from 2). Then you find the GS for the denominator in terms of n. When r=2 (the 3rd term from the left), get a table of the denominators and the n (n starts from 3). Then you find the GS for the denominator in terms of n. When r=3 (the 4th term from the left), get a table of the denominators and the n (n starts from 4). Then you find the GS for the denominator in terms of n. Do the same thing for when r=4 and when r=5. You've got all the general statements in terms of n. Now your goal is to make them to be ONE general statement in terms of r and n. Hint: The general statement is in quadratic form (denominator=an²+bn+c) Tabulate r and the general statements. I am sure you will see some kind of pattern in the values of a, b and c. Find them with a similar method as before, Get a table of a and r. Then you find the GS for a in terms of r. Get a table of b and r. Then you find the GS for b in terms of r. Get a table of c and r. Then you find the GS for c in terms of r. So you've got a, b and c. Put them in the general statement involving n. You will get the GS for the denominator in terms of n and r. This task is fairly easy, though it seems complicated in the beginning. Good luck to all of you!! How do you find the GS after forming a table? I mean I just can't get you! PLease help! Reply Link to post Share on other sites More sharing options...
dessskris Posted June 20, 2011 Report Share Posted June 20, 2011 just do it first.... later then you will see the pattern because the table helps to make the pattern clearer;) Reply Link to post Share on other sites More sharing options...
Procrastination Posted June 20, 2011 Report Share Posted June 20, 2011 I know this is for 2012-2013 but I already started it with my friends however we can't even pass the first point of the first task. How can we get the numerator of the sixth line? Help! Reply Link to post Share on other sites More sharing options...
dessskris Posted June 21, 2011 Report Share Posted June 21, 2011 yes it's for 2012-2013 but it doesn't mean that you'll do the task in year 2012 and 2013 it just means that the task can be used for assessment for students who have their exams in 2012 and 2013 do you see the pattern first or not? if yes then just follow the pattern for the 6th line. Reply Link to post Share on other sites More sharing options...
suli92 Posted June 25, 2011 Report Share Posted June 25, 2011 HelloI've started this portfolio and so far Im still stuck on finding the formula for the denominator.I've read the previous posts but Im still confused? Any help will be much appreciated.( I've come up with a formula but it only gives the first term for the denominators in each row. (numerator-(n-1) Reply Link to post Share on other sites More sharing options...
dessskris Posted June 25, 2011 Report Share Posted June 25, 2011 you've got it for the first term? good then. find it for the 2nd, 3rd and 4th. then generalise it. Reply Link to post Share on other sites More sharing options...
suli92 Posted June 25, 2011 Report Share Posted June 25, 2011 you've got it for the first term? good then. find it for the 2nd, 3rd and 4th. then generalise it. The problem is i cant seem to get to the 2nd and 3rd term. Can you please guide me? Much appreciated. Reply Link to post Share on other sites More sharing options...
dessskris Posted June 25, 2011 Report Share Posted June 25, 2011 you've got it for the first term? good then. find it for the 2nd, 3rd and 4th. then generalise it. The problem is i cant seem to get to the 2nd and 3rd term. Can you please guide me? Much appreciated. sure. but the problem is I don't know what to say if I don't know how far you've gone. do you even see the pattern in the numbers or not? Reply Link to post Share on other sites More sharing options...
suli92 Posted June 25, 2011 Report Share Posted June 25, 2011 (edited) you've got it for the first term? good then. find it for the 2nd, 3rd and 4th. then generalise it. The problem is i cant seem to get to the 2nd and 3rd term. Can you please guide me? Much appreciated. sure. but the problem is I don't know what to say if I don't know how far you've gone. do you even see the pattern in the numbers or not? So far I've managed to obtain a formula for the numerator. I cant seem to find the pattern present for the denominators. The way I looked at it was finding the difference between numerator and denominator. then referring back to the row knowing that the row is 1 less.(numerator-(n-1) Edited June 25, 2011 by suli92 Reply Link to post Share on other sites More sharing options...
dessskris Posted June 25, 2011 Report Share Posted June 25, 2011 ahhh no wonder! no it's not that! do not observe the numerator and the denominator AT THE SAME TIME. no. look at them separately. find the general statement of the numerator ONLY first. when you are completely done then observe the denominator. if it helps, make a new triangle that only shows the denominators, to help you see the pattern better.observe it in each r. when r=1, it's 2, 4, 7, 11. find the general statement in terms of n, and then do the same for other values of r and generalise it. Reply Link to post Share on other sites More sharing options...
suli92 Posted June 25, 2011 Report Share Posted June 25, 2011 How would you actually find this? Is there a method to find it like the numerator. Or do u go through trial and error.Or shear brain power Reply Link to post Share on other sites More sharing options...
dessskris Posted June 25, 2011 Report Share Posted June 25, 2011 what did you do to find the numerator? there are some methods, and the easiest one is the graphical method. if you see the pattern and seriously think about it you'll find a way.sorry if my clues are very vague. don't want to give too much guidance as I'm actually not allowed to. Reply Link to post Share on other sites More sharing options...
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