# Homework Help: Spivak's Calculus Ch.2 Problem 2(i)

1. Mar 18, 2016

### Derek Hart

1. The problem statement, all variables and given/known data
Find a formula for Σ(2i-1) = 1+3+5+...+(2n-1)

Hint: What does the expression have to do with 1+2+3+...+2n?

2. Relevant equations

3. The attempt at a solution
I have tried to solve this on my own for about a day now, and I am having trouble understanding the significance of the hint. I don't want an answer, just advice on how to connect the hint and the original expression.

2. Mar 18, 2016

### axmls

Hint: let $S = 1 + 2 + ... + 2n$ and $Y = 1 + 3 + 5 + ... + (2n - 1)$

Then what is $S - Y$?

3. Mar 18, 2016

### Ray Vickson

Also: how can you find $S-Y$ in terms of $n$?

Last edited: Mar 19, 2016
4. Mar 19, 2016

### Derek Hart

Thanks guys, i finally had an epiphany earlier today with your hints.