Question

I can’t understand the sequence ?o 21o 12o -12o -21

Answer 1

To answer this question, we can proceed as follows:

1. We have that the recursive formula is:

`T_n=T_(n-1)+T_(n-2)`

2. We have that the first term and the second term are, respectively:

`T_1=3,T_2=5`

The third term

Then, to find the third term, we have:

`T_3=T_(3-1)+T_(3-2)\Rightarrow T_3=T_2+T_1`

Now, we have that T1 = 3, and T2 = 5. Therefore:

`T_3=T_1+T_2\Rightarrow T_3=3+5\Rightarrow T_3=8`

Now, we have that: T1 = 3, T2 = 5, T3 = 8.

The fourth term

To find the fourth term, we have:

`T_4=T_(4-1)+T_(4-2)\Rightarrow T_4=T_3+T_2`

Then

`T_4=T_3+T_2=8+5\Rightarrow T_4=13`

Now, we have that T1 = 3, T2 = 5, T3 = 8, T4 = 13.

The fifth term

To find the fifth term, we also have:

`T_5=T_(5-1)+T_(5-2)\Rightarrow T_5=T_4+T_3`

Therefore:

`T_5=13+8\Rightarrow T_5=21`

In summary, therefore, we have that the 5th term of the sequence is 21 (first option).