1. ## Fibonacci series cancellation

I am currently re-viewing some text books of a course I took a few years ago and have come across this Fibonacci relation in the form Fn = Fn+2  Fn+1

F0 = F2 - F1
F1 = F3 - F2
F2 = F4 - F3

Fn = Fn+2  Fn+1

Adding LHS together we get LHS = F0 + F1 + F2 +  + Fn

and RHS = F2 - F1 + F3 - F2 + F4 - F3 +  + Fn+2  Fn+1

And using telescoping cancellation the book states that the RHS = Fn+2 - 1

I can only get the RHS to = Fn+2  Fn+1 - 1 (Because F1 = 1). I am stuck with the  Fn+1 term of the RHS; nothing I can see cancels it out, yet clearly the book states that it has gone. Unfortunately the book doesnt clearly show the cancellation in steps. Anyone here like to help, am I being very dumb???

(sorry about the formatting; I subscripted all the numbers but it doesn't seem to cut and paste into this)

2. Originally Posted by muglyhacker
I am currently re-viewing some text books of a course I took a few years ago and have come across this Fibonacci relation in the form Fn = Fn+2  Fn+1

F0 = F2 - F1
F1 = F3 - F2
F2 = F4 - F3

Fn = Fn+2  Fn+1

Adding LHS together we get LHS = F0 + F1 + F2 +  + Fn

and RHS = F2 - F1 + F3 - F2 + F4 - F3 +  + Fn+2  Fn+1

And using telescoping cancellation the book states that the RHS = Fn+2 - 1

I can only get the RHS to = Fn+2  Fn+1 - 1 (Because F1 = 1). I am stuck with the  Fn+1 term of the RHS; nothing I can see cancels it out, yet clearly the book states that it has gone. Unfortunately the book doesnt clearly show the cancellation in steps. Anyone here like to help, am I being very dumb???

(sorry about the formatting; I subscripted all the numbers but it doesn't seem to cut and paste into this)
HI

$F_0=F_2-F_1$

$F_1=F_3-F_2$

$F_2=F_4-F_3$

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$F_{n-1}=F_{n+1}-F_n$

$F_{n}=F_{n+2}-F_{n+1}$

Just write one more before the last one , then you should be able to see clearly.

3. Ah hah, thank you for that.