Recent content by Enelafoxa

I think i have my way to get out from this confusion sir.. I see that the author of that book derive the equation from ##\sum_{n=1}^N u_n## he took the summation from ##n=1##. So we can use the formula directly only when the summation begin from ##n=1##. So i want to generalized this result for...

I understand what you mean sir... But there is something bothering me from the book... For example : Evaluate the sum $$\sum_{n=1}^N \frac 1 {n(n+2)}$$ Using partial fraction we find $$u_n=-\left[\frac 1{2(n+2)}-\frac 1{2n}\right]$$ Hence ##u_n=f(n)-f(n-2)## with ##f(n)=-\frac 1 {2(n+2)}##, and...

That was my first approach to the problem sir.. But there is something bother me.. From that we get ##f(n)=-\frac 1 {2n^2}## and if we use the formula of ##S_N## we get ##S_N=f(N)-f(0)##. The problem is the function is undefined at ##n=0##. That's why i try to change the original problem.

I forgot to wrote it Sir.. Sorry, my bad... :') ##f(n)## is defined as a function of n such that ##u_n=f(n)-f(n-m)## with m as a 'difference' between the two (i mean like 5-3=2, 5 is differ from 2 by 3, so in this example i have 3 as my 'm'. Sorry i can't be more rigour like a mathemathician...

Of course i will not using formula that i don't understand the meaning of it, i always trying to reproduce it myself.. As long as i can.. :').

Yes Sir, i already derive it by myself. A little different, but it produce the same thing. This is what i got from my derivation ##\sum_{k=1}^m f(N-m+k) - \sum_{k=1}^m f(m-k)## like i wrote above.. I knew what m mean sir..

I just curious about the formula... Is it really work? If it is, is there any exception?

Yes it is K.F Riley and M.P Hobson' book.. Third edition.. Here they are..

Homework Statement Use the diffence method to sum the series ##\sum_{n=2}^N\frac {2n-1}{2n^2(n-1)^2}## Homework Equations from the textbook by Riley i have ##S_N=\sum_{k=1}^m f(N-k+1)-\sum_{k=1}^m f(1-k)## The Attempt at a Solution I prefer to write it as ##S_N=\sum_{k=1}^m...

Can you give the original problem? I can't read your hand writing.. Sorry :(

The Arm of m1g and m2g are different. You Should try again and read the problem carefully.

Thank you so much for your help Berkeman :)

Ups.. Sorry.. I am new here.. Wehre i can Read the guideline?

Thank you Berkeman. May i ask a question? What Should i Study first to learn quantum mechanics by myself? The tuition fee in my country is so high, i can't afford it. But i still want to learn it badly.

hey... I am a new member.. I Love physisc and math.. I Hope i can learn These Subject here. Thank you.