Question

Which is an equation for the nth term of the sequence?

12, 15, 18, 21, ...

Question 1 options:

a)

= 12n + 3


b)

= 3n + 9


c)

= n + 3


d)

= 9n + 3

Answer 1

The answer is a I think

Answer 2

Answer: The correct option is (B)
`a_n=3n+9.`

Step-by-step explanation: We are given to select the equation that represents the nth term of the following sequence :

12, 15, 18, 21, . . .

We see that

the given sequence is an arithmetic one with first term a = 12 and common difference d given by

d = 15 - 12 = 18 - 15 = 21 - 18 = . . . =3.

We know that

the nth term of an arithmetic sequence with first term a and common difference d is given by

`a_n=a+(n-1)d.`

Therefore, the nth term of the given sequence is

`a_n=a+(n-1)d=12+(n-1)*3=12+3n-3=3n+9.`

Thus, the required nth term of the given sequence is
`a_n=3n+9.`

Option (B) is CORRECT.