Use the formula for the general term (the nth term) of a geometric sequence to find the indicated term of the sequence
with the given first term, a1, and common ratio, r.
-Find a9 when $a _ { 1 } = 4 , r = 2$
A) 1024
B) 27
C) 2048
D) 1028

Question

Quizplus · Accepted Answer

The formula for the nth term of a geometric sequence is $a_n = a_1 \cdot r^{(n-1)}$. Plugging in the given values, $a_9 = 4 \cdot 2^{(9-1)} = 4 \cdot 2^8 = 4 \cdot 256 = 1024$.

Use the Formula for the General Term (The Nth Term) a1=4,r=2a _ { 1 } = 4 , r = 2a1​=4,r=2

Use the Formula for the General Term (The Nth Term) $a _ { 1 } = 4 , r = 2$