ab!

I was wondering about ab! (a and b are integers, ! is factorial). Do we first multiply a and b then factorial the product or do we factorial the b and then multiply.

Note by Djordje Marjanovic
5 years, 4 months ago

MarkdownAppears as
*italics* or _italics_ italics
**bold** or __bold__ bold
- bulleted- list
• bulleted
• list
1. numbered2. list
1. numbered
2. list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1paragraph 2

paragraph 1

paragraph 2

[example link](https://brilliant.org)example link
> This is a quote
This is a quote
    # I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
# I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
MathAppears as
Remember to wrap math in $$...$$ or $...$ to ensure proper formatting.
2 \times 3 $$2 \times 3$$
2^{34} $$2^{34}$$
a_{i-1} $$a_{i-1}$$
\frac{2}{3} $$\frac{2}{3}$$
\sqrt{2} $$\sqrt{2}$$
\sum_{i=1}^3 $$\sum_{i=1}^3$$
\sin \theta $$\sin \theta$$
\boxed{123} $$\boxed{123}$$

Sort by:

Depends on the problem statement. Usually either $$(\overline{ab})!, (ab)!, a\cdot b!$$ is given so you don't need to worry. If it is ambigious, ask the composer. But I would treat this as $$(ab)!$$.

- 5 years, 4 months ago

if you are referring to (a*b)! then you should multiply them first and then find the factorial.

- 5 years, 4 months ago

ab! = a(b!) = ab!, and (ab)! = a!b!

- 4 months, 1 week ago

If the problem states explicitly that ab is a two digit number, you should find the factorial of the two digit number. Like $$a=2,b=1$$, calculate 21!.

- 5 years, 4 months ago

You are necessitated to multiply them first and then evaluate the factorial. Think of $$(2*3)!=720$$, and $$2*3!=12$$. See the difference?

- 5 years, 4 months ago