what's the answer:(1*2)+(2*3)+...+(n*(n+1))=?

Question

http://iran-dl.com

n=1000

iran-dl.com is no answer!

Answer 1

The nth term of the series is given by n (n+1).
Tn = n + n^2

Sn = sigma (n) + sigma (n^2)

I hope you know the formulae for sum to first n natural numbers and squares of first n natural numbers. Put in the values and get your answer as (n) (n+1) (n+2)/3

Answer 2

Is that an infinite series, or did YA just cut your question off before the end?

And what's the link/URL for? I am very wary of clicking a link in a YA question or answer, so I won't be clicking your link!

Answer 3

Your series is:

sum( i*(i+1), i=1..n )

Which is:

sum( i^2 + i ) = sum( i^2 ) + sum( i )

The sum(i^2,i=1,n) is simply n*(n+1)*(2n+1)/6.

The sum(i,i=1,n) is simply n*(n+1)/2.

So add the two together and you get:

n*(n+1)*(n+2)/3

For n=1000, this is 334334000.

Answer 4

Hi. Infinity.

Answer 5

nth term is n{n=1}=n^2+n
sum=sigma n^2+sigma n
these are standard expressions

Answer 6

if the ? goes on fore ever the answer is infinity if it stops u need to state the rest of the ? or use a calculaor

Answer 7

no idea!!!!