I don't understand part of a formula

[lunastar]

In chapter 6, there's a bracket-parenthesis thing and I don't understand how you use it. Can you explain?

[yongcheng3315]

Are you talking about the notation for combinations of n things taken r at a time? If so, that is the same as C(m,n), or nCr .

[lunastar]

It was for the number of ways to walk from one corner to another corner of an m by n grid. It's used in several formulas after that too, like Newton's Little Formula.
Also in Pythagorean Triples, how do you find the total of factors/odd factors in x^2?

[yongcheng3315]

Check out here:

http://www.mymathcounts.com/Forum/index.php?topic=250.0

How to find the number of factors? See "twenty more problem solving skills" chapter 2 divisor and divisibility.

[lunastar]

Thanks for the help!