Homework Help: 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

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