# Sigma notation and telescopic problem

1. Nov 20, 2008

### UWMpanther

1. The problem statement, all variables and given/known data
Evaluate the telescoping sum.
a) Sigma i=1 to n [i^4 - (i - 1)^4]

2. Relevant equations
sigma i=1 to n [f(1) - f(i+1)]

3. The attempt at a solution

so i plug in for the eqns. and get 1^4 - n^4

the correct answer should be n^4 but don't know how to get that.

2. Nov 20, 2008

### Vid

You're "relevant equation" doesn't apply to this problem. Just think about it by plugging in the first few terms should be obvious why it's n^4.

3. Nov 20, 2008

### spideyunlimit

DO it again, you'll get 0^4 + n^4

4. Nov 20, 2008

### Vid

Actually, he'll get n^4 - 0^4. Even if they're technically the same thing, you don't want to confuse him more.

5. Nov 20, 2008

### spideyunlimit

Righto! I'm sure the poster will get it, just try again carefully.

6. Nov 21, 2008

### UWMpanther

I kinda understand. I see how the first term becomes n^4 but why is the last 0?

7. Nov 21, 2008

### HallsofIvy

Staff Emeritus
Have you actually written down, say, the first 10 terms?