Question

Write an explicit formula for an, the nth term of the sequence 63, 21, 7,

Answer 1

63/3=21

21/3=7

7/3=7

        -

        3

Answer 2

Answer:

$\Large \boxed{\sf 7 \times 3 ^{3-n}}$

Explanation:

This is a geometric sequence

Use nth term of geometric sequence formula

$a_1 \times r^{n-1}$

Ratio is 27/63=1/3

First term is 63

$\displaystyle 63 \times (\frac{1}{3}) ^{n-1}$

Simplify expression

$\displaystyle 7 \times 3 ^{3-n}$