# Simplifying sigma

• May 6th 2013, 05:50 PM
seal308
Simplifying sigma
Hello I need help with this question:

If f(x) is a funciton of x, defined for all nonnegative integers, simliplify the sum $\sum_{i=1}^n[ (f(i) - f(i-1)]$

My attempt: $\sum_{i=1}^n[f(i)]- \sum_{i=1}^n]f(i-1)]$

Then i kind of expanded f (i-1) in wrongly by saying it's equal to f(i) - f(1).
My final answer is wrong because of this assumption.
Where should I go from here?
• May 6th 2013, 06:32 PM
Prove It
Re: Simplifying sigma
I'd start by writing out the first few terms of each sum. You might see something cool happen...