Nice factorial math

[rasheedaconningham]

Please we need to hear you explain, what you’re doing. My daughter didn’t understand with all that background noise. I appreciate you sharing, please next explain what steps you’re taking.

[Bronze]

Sometimes the long solves doesn't need. Just use each of selection by line. Then you go faster, the answer is 7

[KarlSnyder-jhic]

It's a good problem for me b/c I had to stare at it for a couple minutes to understand where the (x + 2 - 1) came from. Made me wanna go Hmmm . . .
Now the problem is that music running thru my head at 3 AM. 😐

[christopherfreeman]

a simple answer, since x is offset by one in the numerator, and factorials are the same sequence of multiplication of a series of numbers, anything up to x + 1 is canceled out, leaving x + 2 in the numerator. x + 2 = 9. If x was offset by 2 or more, the answer would result from x (x + 1) = 9, and 3 would have a x+2 tacked to the end of the multiplication. All of that simplifies, and you can get a positive answer. That solution is effectively what you did, very nice.

[YujiHatsumi]

Oh
if (x + 2)! = 9
(x + 1)! = 8

put it in:
(x + 2)!
= 9
(x + 1)!

(x + 2) (x + 2 - 1)!
because (x + 2 - 1)! = (x + 1)! = 8 we can use it

(x +2) (x + 1)!
= 9
(x + 1)!

we get (x + 2) = 9
x = 9 - 2 = 7
x = 7 B. is the right answer, i think that's it 😅

i think for the formula we can use:
(x + B) (x + B - A)!
= C
(x + A)!

for get the B we will use A + A

Maybe my way of understanding it is a little strange, so if there is anything wrong, please correct me 😅

[madiospanov]

Если ответ 7, то 7+2=9, а 7+1=8 . Дальше 9/8 не может равно 9 .

[yowvinxfed]

7+2 =9!/ 7+1=8! (Factorial) it turns in to sequence number 9.8! /8! (Factorial). Now you can multiply and divide by 9! (Factory) divided by 8! (Factorial)

[dumitrudraghia]

TREBUIE să știi definiția factorialului: n!=(n-1)!*n, n=2, 3, 4, ....

[sylvesterogbolu-otutu]

If:

9!
---- = 9
8!

(x + 2)! = 9!

x = 7

(x + 1) = 8!

x = 7

[kevinduran]

Math is muscle memory not intelligence, but thanks vanilla mind.

[sailbyzantium]

where does the (x + 2 - 1) come from? Not at all clear.