MHB Serina's questions at Yahoo Answers regarding sigma notation

[MarkFL]

Here are the questions:

How do you write the summation notation for:

1.) 4 - 24 + 144 - 864 + ... ?

2.) summation notation for: 729 + 1000 + 1331 + 1728 + ... + n^3

Here is a link to the questions:

How do you write the summation notation for: 4 - 24 + 144 - 864 + ... ? - Yahoo! Answers

I have posted a link there so the OP can find my response.

 

[MarkFL]

Hello serina,

1.) I would begin by observing the series can be written as:

$$S=4(-6)^0+4(-6)^1+4(-6)^2+\cdots$$

and so we have:

$$S=4\sum_{k=0}^{\infty}(-6)^k$$

2.) I would begin by observing the series can be written as:

$$S=9^3+10^3+11^3+12^3+\cdots+n^3$$

and so we have:

$$S=\sum_{k=9}^n k^3$$

To serina and any other guests viewing this topic, I invite and encourage you to post other pre-calculus problems here in our http://www.mathhelpboards.com/f21/ forum.

Best Regards,

Mark.