# What's this in math?

1. Oct 22, 2012

### lalapnt

in the above pic, (n 0) = 1?? what topic in math is that? i never saw this in my high school math and only saw it in my uni class. i don't know how that is. can someone please help me?

2. Oct 22, 2012

### micromass

They are binomial coefficients. We define

$$\binom{n}{k}=\frac{n!}{k! (n-k)!}$$

You have no doubt seen this before in combinatorics, but with other notation. It is a mystery to me why high school textbooks don't use the $\binom{n}{k}$ notation.

http://en.wikipedia.org/wiki/Binomial_coefficient

3. Oct 22, 2012

### lalapnt

super! and of course i know about binomial coefficients. just like this

thank you very much. now i'm not scared anymore!! :D

4. Oct 22, 2012

### dextercioby

It comes from the convention 0!=1.