Question

If the first three Fibonacci numbers are given as $x_{1} =1$, $x_{2}=1$ and $x_{2} = 2$, what is the value of n for which $x_{n} + x_{n+1}=55$? (see attachment)

Answer 1

Answer:

n = 8

Step-by-step explanation:

Continuing the sequence using

$x_{n}$ + $x_{n+1}$

x₄ = x₂ + x₃ =1 + 2 = 3

x₅ = x₃ + x₄ = 2 + 3 = 5

x₆ = x₄ + x₅ = 3 + 5 = 8

x₇ = x₅ + x₆ = 5 + 8 = 13

x₈ = x₆ + x₇ = 8 + 13 = 21

x₉ = x₇ + x₈ = 13 + 21 = 34

x₁₀ = x₈ + x₉ = 21 + 34 = 55 ← with n = 8

Answer 2

Answer:

The Fibonacci numbers are

1

1

2

3

5

8

13

21

34

55

The eighth Fibonacci Number  is 21, the  ninth  is 34 and the tenth is 55.

So Fibonacci # 8 + Fibonacci Number #9 = Fibonacci# 10

21 + 34 = 55

If you want to read a little bit more about Fibonacci numbers, try this page: http://www.1728.org/fibonacci.htm

that's my website :-)

Step-by-step explanation: