geometric sequence

Question

2,-8,32,-128

Answer 1

the formula is A(n)=a(r)^[n-1] where a=first term and r=common ratio

2, -8, 32, -128, ...

the common ratio r=-4 and a=2

Answer 2

Hi Hunter, the geometric sequence, 2, -8, 32, -128, is created by multiplying each term by -4.

 

2 * -4 = -8

 

-8 * -4 = 32

 

32 * -4 = -128

 

-128 = 512

 

528 * -4 = -2112

 

Questions?

Answer 3

Looking at the sequence, the first number starts with 2. The next 4 numbers are multiplied by 4. 

2 x 4 = 8

8 x 4 = 32

32 x 4 = 128

 

Following that sequence, we get 128 x 4 = 512. We can continue finding out numbers after that.

Hope this helps.

 

Srikanth Srinivasan

Answer 4

To find the common ratio, divide one term by the one before it.

 

-8/2 = -4

 

common ratio is -4.  Every term after is found by multiplying by -4.

Answer 5

The common ratio is -8 / 2, or -4

 

a_n = 2(-4)^n-1