# Please check summation of infinite series?

• Apr 18th 2009, 06:48 PM
pinkprincess08
Please check summation of infinite series?
I need to take the sum of (1/k) - (1/(k+4)) as k--> 1 to infinity

-4/(k(k+4))

• Apr 18th 2009, 06:51 PM
matheagle
Nope.
The k is a dummy variable, the final answer is a number, possibly infinity, free of k.
• Apr 18th 2009, 06:56 PM
pinkprincess08
Okay, so I just did some algebraic manipulation before but, that doesn't get to me the answer...then how do it go about it?
• Apr 18th 2009, 07:11 PM
mr fantastic
Quote:

Originally Posted by pinkprincess08
Okay, so I just did some algebraic manipulation before but, that doesn't get to me the answer...then how do it go about it?

Write out the terms from k =1 to k = 9, say. What do you notice? What do you think is going to happen in the limt of k --> oo.

Add up the terms that are not going to cancel in the limit.
• Apr 18th 2009, 07:35 PM
Calculus26
See attachment only if you haven't figured it out based on Mr fantastic's sage advice.
• Apr 18th 2009, 10:05 PM
pinkprincess08
Sk = 1+(1/2)+(1/3)+(1/4) ?
• Apr 18th 2009, 10:59 PM
matheagle
Quote:

Originally Posted by Calculus26
See attachment only if you haven't figured it out based on Mr fantastic's sage advice.

TYPO...
you must have meant aged not saged advice.
(Giggle)
• Apr 18th 2009, 11:29 PM
mr fantastic
Quote:

Originally Posted by matheagle
TYPO...
you must have meant aged not saged advice.
(Giggle)

Hardy ha ha. You're a fine one to talk, dad. I have googled you, you know. Only moo is allowed to make jokes about my age (because she's the only member [that I'm aware of] who knows what it is within a bull's roar - well, within a sd, anyway).

Anyhow, since things are getting off-topic and the OP has solved the problem, I'll try and make my old athritic fingers type out Thread Clos

• Apr 18th 2009, 11:30 PM
mr fantastic
Quote:

Originally Posted by pinkprincess08
Sk = 1+(1/2)+(1/3)+(1/4) ?

Looks OK (to my aged eyes)