Question

512=-4(-2)^n-1 find n in geometric sequence

Answer 1

n = 8

Explanation:

Rearrange the equation to find n:

512/-4 =
`(-2)^(n-1)`

-128 =
`(-2)^(n-1)`

`(-2)^(7)` = -128

So, n-1 = 7

n = 8

Answer 2

n = 8

Explanation:

512/-4 = -128

-2^? equals -128? Has to be odd since it's negative

-2^1 = -2

-2^3 = -8

-2^5 = -32

-2^7 = -128

But it's -2^n-1 = -128 so you have to add 1

7+1 = 8

So n=8