## anonymous one year ago What is the sum of the geometric sequence 3, 12, 48, … if there are 8 terms?

1. anonymous

@rishavraj

2. rishavraj

see sum of geometric series = $a_1 \times \frac{ r^n - 1 }{ r - 1 }$ where r is common ratio , n is no of terms and a_1 is the first term

3. anonymous

But itsn't it a geometric sequence?

4. rishavraj

yup it is a geometric sequence..i mentioned it ...

5. anonymous

Sorry! You wrote series so I got confused. Anyways, I got 65535 as an answer?

6. rishavraj

yup :))

7. anonymous

Yay! Will you help with one more?

8. rishavraj

yeah :))

9. anonymous

Given the arithmetic sequence an = 6 − 4(n + 2), what is the domain for n?

10. rishavraj

see n is no or terms so it can only hav positive values

11. anonymous

so n>1?

12. anonymous

Thanks:)

13. rishavraj

$n \ge 1$

14. anonymous

yes! Thanks so much:)

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