Question

The first term is 1 in the geometric sequence 1, −3, 9, −27, . . . What is the SEVENTH term of the geometric sequence? Select your answer.
A. −243
B. −30
C. 81
D. 189
E. 729

Answer 1

Answer:

729

Step-by-step explanation:

The first term is 1 in the geometric sequence 1, −3, 9, −27, . .

First find out the nth term formula for the geometric sequence

$a_n=a_1(r)^{n-1}$

where a_1 is the first term =1

r is the common ratio,

$\frac{-3}{1}=-3$

$\frac{9}{-3}=-3$

$\frac{-27}{9}=-3$

r=-3, a_1=1

$a_n=a_1(r)^{n-1}$

$a_n=1(-3)^{n-1}$

Now find out the seventh term, n=7

$a_7=1(-3)^{7-1}=729$