Question

Khaled and Wilma were asked to find an explicit formula for the sequence 1, 3, 9, 27. Khaled said the formula is f(n)=1*3^n-1 and Wilma said the formula is f(n)=1*3^n. Which one of them is right?

Answer 1

ANSWER

$f(n) = 1 \times ( {3}^{n - 1} )$

EXPLANATION

The given sequence is 1, 3, 9, 27...

The first term of this sequence is

$a = 1$

The common ratio is

$r = \frac{3}{1} = \frac{9}{3} = \frac{27}{9} = 3$

The explicit formula for this geometric sequence is

$f(n) = a ( {r}^{n - 1} )$

We substitute the first term and the common ratio to obtain,

$f(n) = 1 ( {3}^{n - 1} )$

Answer 2

Answer:

khaled is correct. f(n)=1x3^n-1

Step-by-step explanation: