A set of n positive number, x1, x2, ...xn, n > = 3
are defined as:
x1=1+(1/x2)
x2=1+(1/x3), etc.
also, xn=1+(1/x1)
Could someone please give me a hint on how to prove that
x1=x2=...xn. If this is the case, then x1 is the golden ratio,
but I can't see how to prove it (which is annoying,because it
seems like it should be something really obvious). For any value
of x1 other than the golden ratio, the sequence appears to
diverge on (though never reach) the golden ratio, meaning that
the series can't be "circular" (not sure what the proper term
is). However, I have no idea how to prove this, and this method
seems too complicated to be the answer to a question such as
this. I also have a formula for xj, but I can't prove this.
My formula is:
xj = -1j+1 Sj x1 +
(-1)j Sj +1
actually, I'm not going to be able to type this out, but
basically, I noticed that when expressing x1, x2, etc. in terms
of x1 the numerator and denominator followed a slightly adapted
version of the Fibonnaci sequence (1,0,1,2,3,5,etc.).
Please could you give me some hints on what kinds of methods to
use. Thanks
Obviously 1,0,1,2,3,5, etc. should actually be 1,0,1,1,2,3,5,etc.
Show that xi -xi+1 = -xi xi+1 (xi-1 -xi ) (where the subscripts are interpreted cyclically if necessary). You can deduce that for any i we have (xi -xi+1 ) = (-1)n x1 2 ...xn 2 (xi -xi+1 ) and the result follows.
a way of proving x1 = x2 = ... = xn is to assume xi>
x(i+1)
=> 1+1/x(i+1) > 1+1/x(i+2)
=> 1/x(i+1) > 1/x(i+2)
=> x(i+1) less than x(i+2)
=> absurdity
now repeat for xi less than x(i+1)
which all => xi=(xi+1)
Alex