In: Advanced Math
For the following exercises, write a recursive formula for each geometric sequence.
Consider the following geometric sequence:
{-2, 4/3, -8/9, 16/27, …} ...... (1)
The first term of above sequence is a1 = 2
Common ratio of the above sequence will be obtained by dividing its second term by the first term,
r = a2 ÷ a1
= 4/3 ÷ (-2)
= -2/3
The recursive formula for a geometric sequence is,
an = ran-1, for n ≥ 2
Substitute r = -2/3, the recursive formula for the nth term of the geometric sequence will be,
an = -2/3an-1, for n ≥ 2
Therefore, the recursive formula for the above geometric sequence is,
a1 = -2
an = -2/3an-1, for n ≥ 2.