Question

1.Given a geometric sequence with a_1=6 and r=2/3, write an explicit formula for a_n, the nth term of the sequence.
2.A geometric sequence has a_4=4 and a_5=7. What is a?

Answer 1

Plug and chug:

http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

Answer 2

ok thanks i get #2 but i still don't understand 1.

Answer 3

an = a1 r^(n-1) = 6 * (2/3)^(n-1)
= 6 * 2(n-1) /3^(n-1)