conbo1990 Posted May 6, 2009 Report Share Posted May 6, 2009 To find the quadratic function, you can simply type in the values of the fishing rod into a graphing calculator (which I am assuming you have!) into the table and hit the quadratic function button and it will give you the equation! The same goes for the cubic function, you just have to hit the cubic function button!I try to do it your way but it doesn't work. It only let me enter X values, not Y values in the table. Can you help me? Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 6, 2009 Report Share Posted May 6, 2009 (edited) I try to do it your way but it doesn't work. It only let me enter X values, not Y values in the table. Can you help me?Being honest, I wouldn't use your calculator as it's a smart plan to plot the graphs of the functions and include them in your coursework. Just enter in the points on Microsoft Excel or something and have it make a graph for you. Much easier too I'm actually not sure how you'd get your calculator to do that, in any case!Similarly, for working it all out (ie the equation you're after), it's perhaps easier to do it using matrices, rather than your calculator, as you can show all the steps of your working out. I recommend using www.bluebit.gr/matrix-calculator, as you can easily include print-outs from it to show your working and hit all the coursework marks. Good luck! Edited May 6, 2009 by Sandwich Reply Link to post Share on other sites More sharing options...
deissi Posted May 6, 2009 Report Share Posted May 6, 2009 Honestly you can't think you'll get full marks by just using regression on your calculator. Reply Link to post Share on other sites More sharing options...
Tilia Posted May 6, 2009 Report Share Posted May 6, 2009 I recommend using www.bluebit.gr/matrix-calculator, as you can easily include print-outs from it to show your working and hit all the coursework marks. Good luck!You have to include that in order to get full marks? Reply Link to post Share on other sites More sharing options...
deissi Posted May 6, 2009 Report Share Posted May 6, 2009 You have to include your calculations there, yes. Reply Link to post Share on other sites More sharing options...
Tilia Posted May 7, 2009 Report Share Posted May 7, 2009 OK. Thanks Reply Link to post Share on other sites More sharing options...
lorna Posted May 10, 2009 Report Share Posted May 10, 2009 hi, could someone please help me:the table only gives data up to the 8th guide, so doesnt that mean I can only work out 8 equations? I can use matrices to find a,b,c,d,e,f,g, which is only a function of x^7. How do I work out functions x^8 and even x^9?Secondly, why is it that i shouldnt be plotting (0,0) as a part of the model? should it only be a constraint/limitation for me to talk about? Or should I make a hybrid function: as in, a function for (0,0) to (1,10), and then a suitable model from the 1st guide onwards?Someone please help asap, it would be greatly appreciated! Reply Link to post Share on other sites More sharing options...
deissi Posted May 10, 2009 Report Share Posted May 10, 2009 Why would you work out a function to x^8 or x^9?There seems to be some confusion as to whether or not (0,0) should be plotted. According to OCC (IB teachers' forum) sources, choosing to abstain from plotting (0,0) is not incorrect, so I would rather suggest that in analyzing your models, you mention how well it fits with the fact that the guide starts at (0,0). Reply Link to post Share on other sites More sharing options...
lorna Posted May 11, 2009 Report Share Posted May 11, 2009 Why would you work out a function to x^8 or x^9?There seems to be some confusion as to whether or not (0,0) should be plotted. According to OCC (IB teachers' forum) sources, choosing to abstain from plotting (0,0) is not incorrect, so I would rather suggest that in analyzing your models, you mention how well it fits with the fact that the guide starts at (0,0).thanks for your help deissi.I'm just wondering, for the parameters which I should discuss, am i talking about the a,b,c,d etc, the coefficients of x which will vary for different functions; OR, am i talking about the range and domain of my model?secondly, what should I be talking about in my Introduction?Thanks in advance! Reply Link to post Share on other sites More sharing options...
Tilia Posted May 11, 2009 Report Share Posted May 11, 2009 Yes, state domain and range and explain WHY they are of that size Reply Link to post Share on other sites More sharing options...
Sandwich Posted May 11, 2009 Report Share Posted May 11, 2009 Thinking of it as a real fishing rod, plotting 0,0 makes no practical sense, anyway. Reply Link to post Share on other sites More sharing options...
NetAN Posted May 20, 2009 Report Share Posted May 20, 2009 can someone help me out with the "define suitable variables, discuss parameters/constraints" part? I've been reading through this whole thread and my teacher tried using matrices, but after looking back on his work for his example (not the real thing), I could resolve the problem and get the same answer, making me very wary of my own work so far.He used these three points: (-4, 0), (-1, 4), (1, 9)and then used the formula ax^2 + bx + c =ythen he made the multiple equations:16a - 4b + c =0a - b + c =4a + b + c =9Then he put them in matrices|16 -4 1| |a| |0||1 -1 1 | |b| = |4||1 1 1 | |c| |9|then he solved for a, b, and c, using wat I'm guessing as taking the inverse of the 3 x 3 matrix and mutiplying it to the 3 x 1 matrix, but I'm not sure.He then gets |2 | as his a,b,c matrix and plugs it back in his equation to the equation y=2x^2 - 2x + 1 |-2| |1 |but when I tried that I got my abc matrix to be |7/30 | |5/2 | |94/15|can someone help me out and tell me how I messed up. The sooner you post, the better. I need the help asap! Reply Link to post Share on other sites More sharing options...
NetAN Posted May 21, 2009 Report Share Posted May 21, 2009 ok, I managed to figure out that my teacher used that answer off the top of his head as an example, but not caculated from his example, so I was doing my work alright anyway. but now I'm stuck on the polynomial part (I tried looking through the whole thread, but it still didn't help me). I've already tried using a 7th-order (7th-order meaning ax^7+bx^6 and so on) equation but it didn't hit all the points. Then I tried using the initial guide at the tip of the rod to make it a 8th-order equation, using the point (0,0) for it, but that ended up with a errror singular mat., meaning the determinate was zero, so no answer could show up. I'm stuck at this point and I really need help asap!!! somone please find it in their heart to respond a.s.a.p. Reply Link to post Share on other sites More sharing options...
Tilia Posted May 21, 2009 Report Share Posted May 21, 2009 Finding a 7th order function is definitely on the right track. Just find it in the same way as the quadratic and cubic. Reply Link to post Share on other sites More sharing options...
NetAN Posted May 22, 2009 Report Share Posted May 22, 2009 thanks, I realized that when I found out I just plugged the numbers in wrong. I'm somewhat stuck now though on what it means by "discuss its reasonableness". What does that mean? Reply Link to post Share on other sites More sharing options...
Tilia Posted May 23, 2009 Report Share Posted May 23, 2009 I discussed how good it was in predicting higher values, I think that's what they mean Reply Link to post Share on other sites More sharing options...
dhruv Posted July 16, 2009 Report Share Posted July 16, 2009 hey ppl,i need help. is there any other way to solve the problem of fishing rod other than the matrices Reply Link to post Share on other sites More sharing options...
Sandwich Posted July 16, 2009 Report Share Posted July 16, 2009 There might be, but I believe the coursework directs you to use matrices...? Reply Link to post Share on other sites More sharing options...
dhruv Posted July 16, 2009 Report Share Posted July 16, 2009 we can either use matrices or any other method, i have figured out that using a graphical calculator we can create a simultaneous equation of 3 degree and solve it. Reply Link to post Share on other sites More sharing options...
Sandwich Posted July 16, 2009 Report Share Posted July 16, 2009 Remember you get points for working out and method. In all honesty, it's so easy to use the matrix method, you should probably use it just to be safe. 1 Reply Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.