Question

Sebastian writes the recursive formula f(x+1) = 4f(x) to represent a geometric sequence whose second term is 12. Which explicit formula can be used to model the same sequence?

Answer 1

B.) f(x) = 3(4)x − 1

Explanation:

Answer 2

B.) f(x) = 3(4)x − 1

Explanation:

A) f(x) = 12(4)x

B.) f(x) = 3(4)x − 1

C.) f(x) = 4(12)x

D.) f(x) = 4(3)x − 1

Given:

f(x+1) = 4f(x)

f(2)=12

f(2) = 12

f(3) = 4f(2) = 4 * 12 = 48

f(3)=48 and f(2)=12

From f(3)=48 and f(2)=12

r=48/12

=4

r=common ratio

Recall,

f(2)=12=ar

r=4

f(2)=ar=12

a*4=12

a=12/4

a=3

an=ar^(n-1)

For x term

an=3*4(x-1)

B.) f(x) = 3(4)x − 1