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odolwa99
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Homework Statement
Hi! This is my first time on the site. I look forward to working with everyone…but hopefully not too much, assuming I‘m learning things correctly. :P
My question pertains to Recurrence Relations, so here it goes…
Foreword: The textbook I’m using actually supplies the answer to the question, so I already have a point of reference, but my attempt does not match up with the answers. I believe my approach is essentially correct, as it has yielded the correct answers for a similar question beforehand. Answer is: 1, 3, 7, 17, 41
Please note that I am beginning the question from u3, as we already have the values for u1 and u2.
Homework Equations
Q. Find the first five terms of the sequence:
u1 = 1, u2 = 3 and un = 2un-1 + un-2
The Attempt at a Solution
Attempt:
Solve un+1 where un = 3un-1 - un-2
=> 3u(n+1)-1 - u(n+1)-2
Begin by substituting 3 (i.e. u2) for un:
If n = 1 then u3 = 2((3+1) - 1) + ((3+1) -2) => 2(4-1) + (4-2) => 6 + 2
Ans.: u3 = 8... but should be 7!
Proceeding with u3 as 7, not 8...
If n = 2 then u4 = 2((7+1) -1) + ((7+1) -2) => 2(8-1) + (8-2) => 14 + 6
Ans.: u4 = 20... But should be 17!
Note, I am omitting solution of u5 for brevity’s sake.
I‘m sure the answer is staring me in the face, but I just can’t seem to figure it out!
Can anyone help?
Thanks.
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