# Calculus

How many terms are required in the series (-6) + (-12) + (-24)... to add to a sum of -378?

How do I do this?

1. 👍 0
2. 👎 0
3. 👁 130
1. looks like a geometric series where
a = -6 and r = 2
Term(n) = a(r^n - 1)/(r-1), where n is the number of terms
-378 = -6(2^n - 1)/(2-1)
63 = 2^n - 1
64 = 2^n
I know that 2^6 = 64
so n=6

so you need 6 terms.

1. 👍 0
2. 👎 0

1. 👍 0
2. 👎 0

## Similar Questions

1. ### math

The sum of the 1st nine terms of an arithmetic series is 216. The 1st,3rd and the 7th terms of series form the 1st three terms of a geometric series. Find the 1st term and the constant difference of the arithmetic series ?

2. ### math

The sum of the first 5 terms of an arithmetic series is 70. The sum of the first 10 terms of this arithmetic series is 210. What is the first term of the series?

3. ### math

the question is find the sum of the first eight terms in the series 3-12+48-192+... is 1)-13,107 2)-21,845 3)-39,321 4)-65,535 I got that a1 is 3 and a8 was -49152. I wanted to make sure this was a geometric sequence with a r of

4. ### Math

For the geometric series, S4/S8 = 1/17. Determine the first three terms of the series if the first term is 3.

1. ### math

in a geometric series t1=23,t3=92 and the sum of all of the terms of the series is 62 813. how many terms are in the series?

2. ### calculus

Use multiplication of power series to find the first three non-zero terms of the Maclaurin series of e^x ln(1 − x).

3. ### Math

The first two terms in a geometric series is 12. The sum of the first three terms of the same series is 62. Determine the first four terms of the series.

4. ### Math

If S1 = 0.7 and S2 = 2.1 in a geometric series, determine the sum of the first 12 terms in the series. Be sure to show all of your work.

1. ### Arithmetic Series - - Reiny

Consider the series defined by Sn = 3n-1 Find the first four terms of the series. How exactly do I do this?

2. ### English

help please 1.Use the sentence to answer the question. We are excited for summer vacation, for we have plans to visit several national parks. Which comma rule is used in the sentence? (1 point) a.compound sentence b.items in a

3. ### Math question

In an arithmetic series, the 15th term is 43 and the sum of the first 15 terms is 120. Add the first 20 terms of the series.

4. ### Calculus - - Reiny

If S1 = 0.7 and S2 = 2.1 in geometric series, what would the sum of the first 12 terms in the series be? I tried doing this, and I got 1.16 or something :S How exactly do I do this? Please tell me what formula to use. I was using