What is the 7th term of the geometric sequence where a1 = 1,024 and a4 = −16?

Verified Answer :

irspow

-16=ar^4 divided by 1024=ar is:

-1/64=r^3

r=-1/4

1024=a(-1/4), a=-4096 so

a(n)=-4096(-0.25^n)

a(7)=-4096(-0.25^7)=0.25

Answer:

the 7th term of the geometric sequence is 1/4  or 0.25

Step-by-step explanation:


Given geometric sequence terms

a1 = 1,024 and a4 = −16

nth term of geometric sequence is

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

a1 = 1,024 and a4 = −16

Plug in 4 for n and solve for 'r'

\(a_4= a_1(r)^{4-1}\)

\(-16= 1024(r)^{3}\)

Divide both sides by 1024

\(\frac{-1}{64} = r^3\)

Now take cube root on both sides

\(\frac{-1}{4} = r\)

To find 7th term we plug in n=7 , r= -1/4 , a1 = 1024

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

\(a_7= 1024(-1/4)^{7-1}\)

\(a_7= 1024(-1/4)^{6}\)

a_7 = 0.25