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.

Easy Math Editor

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`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
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Comments

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 $(ab)!$ .

Zi Song Yeoh - 8 years, 1 month ago

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

Sudha Parimala - 8 years, 1 month ago

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

Vaibhav Priyadarshi - 3 years, 1 month 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!.

Aditya Parson - 8 years, 1 month 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?

Shourya Pandey - 8 years, 1 month ago

Math	Appears 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}`	$\boxed{123}$