Question

Write the first five terms of the sequence defined by the recursive formula

Answer 1

Answer: the corrrect one is A s9=9/2(2+26)

Answer 2

The correct answer option is:
`S_9=(9)/(2) (2+26)`

Explanation:

We know that,

the sum of the first
`n` terms of an Arithmetic Sequence is given by:

`S_9=(n(a_1+a_n))/(2)`

where
`n` is the number of terms,

`a_1` is the first term of the sequence; and

`a_n` is the first term of the sequence.

So for
`a_n=3n-1`,

`a_1=3(1)-1=2`

and

`a_9=3(9)-1=26`

Putting these values in the formula to get:

`S_9=(9(a_1+a_9))/(2)`

`S_9=(9(2+26))/(2) \\\\S_9=(9)/(2) (2+26)`

First five terms:

`a_1=3(1)-1=2`

`S_1=(1(2+2))/(2)`=2

`a_2=3(2)-1=5`

`S_2=(2(2+5))/(2)`=7

`a_3=3(3)-1=8`

`S_2=(3(2+8))/(2)`=15

`a_4=3(4)-1=11`

`S_4=(4(2+11))/(2)`=26

`a_5=3(5)-1=14`

`S_5=(5(2+14))/(2)`=40