Reminds me of broccoli

Algebra Level 3

Matthew has a magical Fibonacci tree, which grows in the following pattern:

  • During the 1 st 1^\text{st} day, it only has one branch (i.e. the main trunk).
  • During the 2 nd 2^\text{nd} day, it grows F 2 + 1 F_{2+1} branches on the initial 1 branch.
  • During the 3 rd 3^\text{rd} day, it grows F 3 + 1 F_{3+1} branches on each of the F 2 + 1 F_{2+1} branches ( ( newly grown during the 2 nd 2^\text{nd} day ) . ).
  • During the ( n + 1 ) th (n+1)^\text{th} day, it grows F ( n + 1 ) + 1 F_{(n+1)+1} branches on each of the F n + 1 F_{n+1} branches ( ( newly grown during the n th n^\text{th} day ) . ).

His neighbor, Olivia, thinks that the tree is blocking her sunlight, so cuts 1 1 branch on the 3 rd 3^\text{rd} day as a start. Then she multiplies the number of branches she cuts by x x each following day. But no matter how many days she does this, the branches never seem to stop growing.

Find the maximum value of x x such that the above scenario is possible. If there is no solution, input your answer as 0 0 .

Details and Assumptions:

  • Olivia will start cutting from the newly grown branches. A branch is counted new if it is less than 1 day old.
  • During the 3 rd 3^\text{rd} day, she cuts 1 1 newly grown branch, so Mark will be left with 6 1 = 5 6-1=5 new branches. During the 4 th 4^\text{th} day, the remaining 5 5 branches will each grow F 4 + 1 = 5 F_{4+1} =5 new branches, resulting in 25 25 new branches. On the same day, Olivia cuts x 1 x^{1} branches, so 25 x 25-x branches remain. And the pattern continues...
  • If the branches newly grown on the n th n^\text{th} day are all cut, the previous "new" branches will grow F n + 1 F_{n+1} branches.

Bonus: Explain why.


The answer is 8.

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