Posted by Cody Libby on Tuesday, August 30, 2011 at 1:10am.
Please write exact formula.
I think I am looking at a repeating "continued fraction"
let x = 5+3/(5+3/(5+3/(5+3/(.....
now look at the part that I put in bold
x = 5+3/(5+3/(5+3/(5+3/(.....
Isn't the part in bold the same as the original x ?
(since it also goes to infinity, it would not matter at which 5 you start)
so we have
x = 5 + 3/x
x^2 = 5x + 3
x^2 - 5x - 3 = 0
x = (5 ± √(25 - 4(1)(-3))/2
= (5 + √37)/2 , rejecting the negative answer, since obviously the expression is positive, with only positive numbers showing up
so 5+3/(5+3/(5+3/(5+3/(..... = (5+√37)/2
check: my result is appr equal to 5.54139...
using : 5 + 3/5 = 5.6
using : 5 + 3/(5+3) = 5.375
using : 5 + 3/(5 + 3/5) = 5.53714..
using : 5 + 3/(5 + 3/(5 + 3)) = 5.55814..
notice that each consecutive result converges on my exact answer of
(5+√37)/2 , once above it, then below it, the difference getting smaller each time.
thank you very much for your help. i was stuck on what value to put as x
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