4) If the first three Fibonacci numbers are x, = 1, .x = 1, x3 = 2,
what is the value of n for which .x. +x... + x = 68?

The value of n for which xₙ₋₂ + xₙ₋₁ + xₙ = 68 is n = 9

Step-by-step explanation:

The nth term of Fibonacci number is given by the following relation;

Given that we have ;

When n = 3, we have;

∑xₙ = 4

When n = 4 we have

∑xₙ = 4

When n = 6 we have

∑xₙ = 16

When n = 9 we have

∑xₙ = 68

Therefore, we have the value of n for which xₙ₋₂ + xₙ₋₁ + xₙ = 68 is n = 9.