Arithmetic,Geometric

Question

Using your formula from the previous question, find the 15th term of the sequence   2, 6, 18, 54, ...

The 15th term is[                  ]

(no commas in your answer please - just the number!)

Answer 1

a1 = 2

a2 =2(3)

a3 =2(3)^2 = 18

a4 =2(3)^3 = 54

...

a15 = 2(3)^(15-1) = 2(3)^14 = 9,565,938 = 9565938 if you don't like commas. Use a calculator to find the value of 3^14.

...

an = 2(3)^(n-1) is the general formula for any n where n can be any integer from 1 to infinity.