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October 6th, 2008, 06:24 AM  #1 
Newbie Joined: Sep 2008 Posts: 11 Thanks: 0  Homogeneous Second?Order Difference Equations
Alright...it is me again...and more to come... sorry... I am really bad in math.. Can someone help me understand everything after the general solution? Why is 2A + 2B and 7A + 2B? Is there a formula to follow? is (1) always minus (2)? Where does the 9A comes from? Basically everything after General Solution. Thanks... 
October 6th, 2008, 10:15 AM  #2  
Senior Member Joined: Jul 2008 Posts: 895 Thanks: 0  Re: Homogeneous Second?Order Difference Equations Quote:
 
October 6th, 2008, 05:10 PM  #3 
Newbie Joined: Sep 2008 Posts: 11 Thanks: 0  Re: Homogeneous Second?Order Difference Equations
Yes, Dave, I need to take this course, to understand this and to pass this..I am bad in this, that is why I need to learn.Sometimes in life we just can't choose what we want or do not want.. 
October 6th, 2008, 06:22 PM  #4 
Senior Member Joined: Jul 2008 Posts: 895 Thanks: 0  Re: Homogeneous Second?Order Difference Equations
You have [had] found the general solution... You are told that ... This means that n = 2, so sub that into the general solution: What you seem not to know is that an exponent of 0 implies a value of 1. That is... 2 = A*1 + 2B*1 or A + 2B = 2 Similarly with... substitute 1 for n: That is 31 = 7A + 2B What you now have is a system of two equations in A and B, and can solve for them. My point is that all of this, including solving the two eqations is studied where I live in grade 9. Your studies should have had you master this and then much more before you started your present study which is a leadin for studies in differential equations. My remarks were based upon the indicated lack of this firm background would mean that you will have to continually reach back into those studies and that can be overpowering in advanced studies that require this understanding already. I'm not saying to give up, and in fact wish you well. I am saying to get back to those precourses and take a fresh look at what you might be missing. That will require a good deal of effort. You need to be able to dogpaddle REALLY well if going into the deeper water. All I can add is "Good luck", and mean it sincerely. 
October 6th, 2008, 06:23 PM  #5 
Senior Member Joined: Jul 2008 Posts: 895 Thanks: 0  Re: Homogeneous Second?Order Difference Equations
You have [had] found the general solution... You are told that ... This means that n = 0, so sub that into the general solution: What you seem not to know is that an exponent of 0 implies a value of 1. That is... 2 = A*1 + 2B*1 or A + 2B = 2 Similarly with... substitute 1 for n: That is 31 = 7A + 2B What you now have is a system of two equations in A and B, and can solve for them. My point is that all of this, including solving the two equations is studied where I live in grade 9. Your studies should have had you master this and then much more before you started your present study which is a leadin for studies in differential equations. My remarks were based upon the indicated lack of this firm background would mean that you will have to continually reach back into those studies and that can be overpowering in advanced studies that require this understanding already. I'm not saying to give up, and in fact wish you well. I am saying to get back to those precourses and take a fresh look at what you might be missing. That will require a good deal of effort. You need to be able to dogpaddle REALLY well if going into the deeper water. All I can add is "Good luck", and mean it sincerely. 
October 6th, 2008, 08:17 PM  #6 
Newbie Joined: Sep 2008 Posts: 11 Thanks: 0  Re: Homogeneous Second?Order Difference Equations
Hi Dave, Thanks...I really appreciate it. Anyway, I am currently doing my degree in InfoComm Technology and am quite surprise that I have to clear this Further Discrete Maths course.

October 7th, 2008, 04:19 AM  #7  
Senior Member Joined: Jul 2008 Posts: 895 Thanks: 0  Re: Homogeneous Second?Order Difference Equations Quote:
So .... DO take a fresh look a some past material [elementary algebra geometry trig] and try to get through it better than you did before. It's always worth the effort to skip a few nights in the pub.  
October 8th, 2008, 06:37 PM  #8  
Newbie Joined: Sep 2008 Posts: 11 Thanks: 0  Re: Homogeneous Second?Order Difference Equations Quote:
 
October 12th, 2008, 10:00 PM  #9 
Newbie Joined: Sep 2008 Posts: 11 Thanks: 0  Re: Homogeneous Second?Order Difference Equations
Hey..one more thing...I came across this while trying to solve the equation. May I know how am I suppose to get 2pine/3?

October 14th, 2008, 01:39 AM  #10 
Global Moderator Joined: Dec 2006 Posts: 20,469 Thanks: 2038 
That's the external angle of an equilateral triangle, so consider the geometry of such a triangle.


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difference, equations, homogeneous, secondorder 
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