What does "n over 1 without a line between" signify?

Question

I'm starting to work my way through Algebra I by Jacobson after being out of college for 15 years, and he's using an expression I don't remember from college algebra.

It's a number over a number without a line between. I assume it means "n divided by 1", is this correct?

Here's a scan of the expression:

binomial coefficient. In general $\binom{n}{k}=\frac{n!}{k!(n-k)!}$ so $\binom{n}1=\frac{n!}{1!(n-1)!}=n$. Another notation is $C(n,k)$. You often find that on calculators. — drhab, Aug 01 '16 at 15:40

score 5 · Accepted Answer · answered Aug 01 '16 at 15:39

5

The symbol ${n \choose k}$ is called a binomial coefficient, and it is read as "n choose k". It is the number of ways to choose $k$ objects, unordered, from a collection of $n$ objects. It is equal to $\frac{n!}{k!(n-k)!}$, where "!" denotes factorial.

answered Aug 01 '16 at 15:39

Ian

101,645

Bonus for the factorial tidbit – Jack Steam Aug 01 '16 at 16:13

What does "n over 1 without a line between" signify?

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