eel7x6 Posted March 30, 2008 Report Share Posted March 30, 2008 I am doing my Maths portfolio on investigating divisibility atm. I am really stuck on question 3 and 4. These are the portfolio questions 1. Factorize the expression P(n)=n^x-n for x = 2,3,4,5. Determine if the expression is always divisible by the corresponding x. If divisible use mathematical induction to prove your result by showing whether P(k+1)-P(k) is always divisible by x. Using appropriate technology, explore more cases and make a conjecture for when n^x - n is divisible by x. 2. Explain how to obtain the entries in Pascal's triangle...State the relationship between the expression P(k+1)-P(k) and Pascal's traingle. Reconsider your conjecture. Write an expression for the xth row of the Pascal's Triangle. You will have noticed that (x r) = k, k is a natural number. Determine when k is a multiple of x. 3. Make conclusions regarding the last result in part 2 and the form of proof by inductiton used in this assignment. Refine your conjecture if neccessary, and prove it. 4. State the converse of your conjecture. Describe how you woul prove whether or not the converse holds. The ones in bold are the questions I dont get, especially the 3rd and 4th question. (what is converse?) The italic part - I do not know how to use words to describe it... Plz help it is due this wednesday!!! Reply Link to post Share on other sites More sharing options...
Scade Posted March 30, 2008 Report Share Posted March 30, 2008 I've done the same IA about a month ago, but don't know how went it well. Anyway I'll try to provide some hints Writing the expression for the xth row is just basically writing the expression you would use to get any row in pascal's triangle (provided you're using the n C r method). In the next part k stands for just a standard coefficient. If you've done the previous parts correctly it should be pretty obvious when k is a multiple of x. Again if you've done everything correctly up to part 3 the conclusions you make should be pretty obvious (it relates directly to your conjecture). I wasn't quite sure what they meant with the part of making conclusions about the form of proof by induction. Anyway I talked about the restrictions it places, when it is generally used and that kind of stuff. Refining your conjecture should be pretty obvious and proving it is also rather easy. You should check converse from some dictionary. Basically it is on accordance with your conjecture, and just derived from it. As a general advice you might want to do some search in the internet. At least it helped me quite a lot. Remember just not to copy anything, only see what information you find and then think how you can apply it. Reply Link to post Share on other sites More sharing options...
eel7x6 Posted March 30, 2008 Author Report Share Posted March 30, 2008 for the second part of the 2nd question, I said k is a multiple of x when x is a prime number. is that right? Reply Link to post Share on other sites More sharing options...
Scade Posted March 30, 2008 Report Share Posted March 30, 2008 Yup, that was my statement also. In the end if you do the questions in order it should sort of open up by itself. Reply Link to post Share on other sites More sharing options...
diabolicalangle Posted April 2, 2008 Report Share Posted April 2, 2008 (edited) nmv, im being a dunce Edited April 5, 2008 by diabolicalangle Reply Link to post Share on other sites More sharing options...
Scade Posted May 8, 2008 Report Share Posted May 8, 2008 i need help on this topic tooo Please ask specifically what kind of help you need. I don't think anyone will be able to provide help when it is not specified where you need help Reply Link to post Share on other sites More sharing options...
appleme Posted May 9, 2008 Report Share Posted May 9, 2008 (edited) 4. State the converse of your conjecture. Describe how you woul prove whether or not the converse holds.The ones in bold are the questions I dont get, especially the 3rd and 4th question. (what is converse?)I really need help with this bit too... a converse is the opposite - so i think that if your conjecture is: all even numbers have the letter e in them (silly example i know), the converse would be numbers that have the letter e are even... can anybody verify this?and when it says describe how you would prove it instead of prove it i really dont know what they are asking for! do you say something like i would try each number? because that just sounds silly Edited May 9, 2008 by appleme Reply Link to post Share on other sites More sharing options...
Amuh Posted May 10, 2008 Report Share Posted May 10, 2008 please some one post sumfn more on this topic...please please i also need help...i am stuck with the first point... Reply Link to post Share on other sites More sharing options...
appleme Posted May 11, 2008 Report Share Posted May 11, 2008 please some one post sumfn more on this topic...please please i also need help...i am stuck with the first point... the first one? its basically looking at each n^2-n, n^3-n etc. and proving it works by induction... Reply Link to post Share on other sites More sharing options...
Amuh Posted May 14, 2008 Report Share Posted May 14, 2008 can some one here send me a copy of what they did..i just want to get a rough idea..coz i am duffer in math HL Reply Link to post Share on other sites More sharing options...
Camlon Posted May 19, 2008 Report Share Posted May 19, 2008 (edited) Do any of you know how to prove the converse? I'm able to prove 3, but the converse is much harder. Edited May 19, 2008 by Camlon Reply Link to post Share on other sites More sharing options...
Scade Posted May 19, 2008 Report Share Posted May 19, 2008 If you look at the wording, it doesn't say that you need to prove it, just state how you would do it. My hint is to not use induction, but contradiction. Reply Link to post Share on other sites More sharing options...
Camlon Posted May 19, 2008 Report Share Posted May 19, 2008 (edited) Yeah, but shouldn't I at least tell how to do it generally, or could I just write. To prove that Q=p(k 1))- p(k) is not divisible by x, use proof by contridiction and assume that evey term of Q is divisible and then end up with a contridiction. I didn't really use induction for 3 either, I just proved it and found a way to make it a proof with induction. Edited May 19, 2008 by Camlon Reply Link to post Share on other sites More sharing options...
Camlon Posted May 21, 2008 Report Share Posted May 21, 2008 I showed that it was not true for x=561, using Little Theorem of Fermat. Everybody was expecting it to be true, but it's not. As I'm the only further maths student at my school I think I'm the only one who got that. Reply Link to post Share on other sites More sharing options...
pdenny29 Posted October 1, 2008 Report Share Posted October 1, 2008 I showed that it was not true for x=561, using Little Theorem of Fermat. Everybody was expecting it to be true, but it's not. As I'm the only further maths student at my school I think I'm the only one who got that.561 actually isn't prime and wouldn't work. Reply Link to post Share on other sites More sharing options...
shrekmak Posted October 1, 2008 Report Share Posted October 1, 2008 no, this guy has a point.561 is a counter example for the converse of your conjecture.do some research.... omg, he just saved me 10pts. Reply Link to post Share on other sites More sharing options...
nba favor Posted October 2, 2008 Report Share Posted October 2, 2008 I've done the same IA about a month ago, but don't know how went it well. Anyway I'll try to provide some hints Writing the expression for the xth row is just basically writing the expression you would use to get any row in pascal's triangle (provided you're using the n C r method). In the next part k stands for just a standard coefficient. If you've done the previous parts correctly it should be pretty obvious when k is a multiple of x.Again if you've done everything correctly up to part 3 the conclusions you make should be pretty obvious (it relates directly to your conjecture). I wasn't quite sure what they meant with the part of making conclusions about the form of proof by induction. Anyway I talked about the restrictions it places, when it is generally used and that kind of stuff. Refining your conjecture should be pretty obvious and proving it is also rather easy.You should check converse from some dictionary. Basically it is on accordance with your conjecture, and just derived from it.As a general advice you might want to do some search in the internet. At least it helped me quite a lot. Remember just not to copy anything, only see what information you find and then think how you can apply it.What is actually the relationship between the expression P(k+1)-P(k) and Pascal's Triangle? Reply Link to post Share on other sites More sharing options...
AlphaMagnum Posted November 9, 2008 Report Share Posted November 9, 2008 I'm having a bit of trouble with the second two questions on this one, but I'll put up the full set before I get to that.Factorize the expression P(n) = n^(x) - n for x {2,3,4,5}. Determine if the expression is always divisible by the corresponding x. If divisible use mathematical induction to prove your results by showing whether P(k+1) - P(k) is always divisible by x. Using appropriate technology, explore more cases, summarize your results, and make a conjecture for when n^(x) is divisible by x.Explain how to obtain the entries in Pascal's Triangle, and using appropriate technology, generate the first 15 rows. State the relationship between the expression P(k+1) - P(k) and Pascal's Triangle. Reconsider your conjecture and revise if necessary. Write an expression for the xth row of Pascal's Triangle. You will have noticed that nCr(x,r) = k, k is a natural number. Determine when k is a multiple of x.Make conclusions regarding the last result in Part 2 and the form of proof by induction used in this assignment. Refine your conjecture if necessary, and prove it.State the converse of your conjecture. Describe how you would prove whether or not the converse holds.I've gotten through numbers 1 and 2, and my two problems with those were:How do I appropriately use technology? Do you have any suggestions for how best to show that I used it?Starting from #1, I said that the expression is divisible when x is prime, so do I just say that the Pascal's Triangle results are in accordance with that conjecture?I'm stuck on numbers 3 and 4 entirely, because I'm not entirely sure as to what they're asking.For 3:I can talk about proof by induction and why it works here but not necessarily elsewhere.I'm not sure about what kind of conclusions they want me to make.I'm still looking at how I'd like to prove it, but I'm not sure if I should use a proof by contradiction (need to figure out how first) or some other type.For 4:This question doesn't actually ask for much, so I'm thinking that I should be fine with it once I determine a neat statement of my conjecture from which I can find the converse.Any help with this would be really appreciated,AlphaMagnum Reply Link to post Share on other sites More sharing options...
pumpkinora Posted November 16, 2008 Report Share Posted November 16, 2008 I am doing my Maths portfolio on investigating divisibility atm. I am really stuck on question 3 and 4.These are the portfolio questions1. Factorize the expression P(n)=n^x-n for x = 2,3,4,5. Determine if the expression is always divisible by the corresponding x. If divisible use mathematical induction to prove your result by showing whether P(k+1)-P(k) is always divisible by x. Using appropriate technology, explore more cases and make a conjecture for when n^x - n is divisible by x.2. Explain how to obtain the entries in Pascal's triangle...State the relationship between the expression P(k+1)-P(k) and Pascal's traingle. Reconsider your conjecture.Write an expression for the xth row of the Pascal's Triangle. You will have noticed that (x r) = k, k is a natural number. Determine when k is a multiple of x.3. Make conclusions regarding the last result in part 2 and the form of proof by inductiton used in this assignment. Refine your conjecture if neccessary, and prove it.4. State the converse of your conjecture. Describe how you woul prove whether or not the converse holds.The ones in bold are the questions I dont get, especially the 3rd and 4th question. (what is converse?) The italic part - I do not know how to use words to describe it...Plz help it is due this wednesday!!! Reply Link to post Share on other sites More sharing options...
pumpkinora Posted November 16, 2008 Report Share Posted November 16, 2008 I'm having a bit of trouble with the second two questions on this one, but I'll put up the full set before I get to that.Factorize the expression P(n) = n^(x) - n for x {2,3,4,5}. Determine if the expression is always divisible by the corresponding x. If divisible use mathematical induction to prove your results by showing whether P(k+1) - P(k) is always divisible by x. Using appropriate technology, explore more cases, summarize your results, and make a conjecture for when n^(x) is divisible by x.Explain how to obtain the entries in Pascal's Triangle, and using appropriate technology, generate the first 15 rows. State the relationship between the expression P(k+1) - P(k) and Pascal's Triangle. Reconsider your conjecture and revise if necessary. Write an expression for the xth row of Pascal's Triangle. You will have noticed that nCr(x,r) = k, k is a natural number. Determine when k is a multiple of x.Make conclusions regarding the last result in Part 2 and the form of proof by induction used in this assignment. Refine your conjecture if necessary, and prove it.State the converse of your conjecture. Describe how you would prove whether or not the converse holds.I've gotten through numbers 1 and 2, and my two problems with those were:How do I appropriately use technology? Do you have any suggestions for how best to show that I used it?Starting from #1, I said that the expression is divisible when x is prime, so do I just say that the Pascal's Triangle results are in accordance with that conjecture?I'm stuck on numbers 3 and 4 entirely, because I'm not entirely sure as to what they're asking.For 3:I can talk about proof by induction and why it works here but not necessarily elsewhere.I'm not sure about what kind of conclusions they want me to make.I'm still looking at how I'd like to prove it, but I'm not sure if I should use a proof by contradiction (need to figure out how first) or some other type.For 4:This question doesn't actually ask for much, so I'm thinking that I should be fine with it once I determine a neat statement of my conjecture from which I can find the converse.Any help with this would be really appreciated,AlphaMagnumHi guys.I too am stuck and am not sure where to start on number one. Can anyone point me in the right direction...not looking for the answer, just some guidance. Mine's due in tomorrow.HELP Reply Link to post Share on other sites More sharing options...
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