Question

Write an explicit formula for an arithmetic sequence whose common difference is -3, and first term is -9.

Answer 1

Answer:

The required formula is $a_n =-3n-6$.

Step-by-step explanation:

Given : An arithmetic sequence whose common difference is -3, and first term is -9.

To find : Write an explicit formula for an arithmetic sequence ?

Solution :

An explicit formula for an arithmetic sequence is given by, $a_n = a_1 +d(n -1)$

Where, $a_n$ is the nth term of the sequence

$a_1=-9$ is the first term of the sequence

d=-3 is the common difference

n is the number terms

Substitute the value in the formula,

$a_n =(-9)+(-3)(n -1)$

$a_n =-9-3n+3$

$a_n =-3n-6$

Therefore, the required formula is $a_n =-3n-6$.

Answer 2

Answer:

  an = -9 -3(n -1)

Step-by-step explanation:

The explicit formula for an arithmetic sequence with first term a1 and common difference d is ...

  an = a1 +d(n -1)

Putting your numbers into the formula gives ....

  an = -9 -3(n-1)