Question

Find the 12th term of the geometric sequence 2,-4,8…

Answer 1

-4096

Explanation:

Formula of geometric sequence is

`a _(1) (r {}^(n - 1) )`

where a1 is the first term of geometric series, R is the common ratio and n is the nth term of the sequence.

the first term is 2 so a1=2

Common ratio is -2

N term is 12

`2( - 2 {}^(12 - 1) ) = 2( - 2 {}^(11) )`

So we get

`- 4096`

Answer 2

Explanation:

Hi there!

The given geometric sequence is: 2,-4,8.....

Then,

1st term = 3

Common ratio = t2/t1

= -4/2

= -2

We have,

General term of geometric sequence = a*
`r^(n-1)`

Where "n" is no. of terms

an = a*
`r^(n-1)`

or, a12 = 2*
`-2^(12-1)`

= 2*-2048

= -4096

Therefore, the 12th term is -4096.

Hope it helps!