How can I write this sequence in terms of factorials?

In summary, the conversation is about finding an expression for n((n^2)-1) in terms of factorials. The correct answer is (n+1)!/(n-2)!. The conversation includes a hint to expand the numerator and denominator and cancel out the common factors.
  • #1
martinrandau
9
0
Can anybody help me solving this?

Write in terms of factorials

n((n^2)-1)

The correct answer is
(n+1)!/(n-2)!

but I don't know how to get there, and since it's week- end I have no chance to ask anyone teachers, etc.
//Martin
 
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  • #2
n(n2-1) = n(n-1)(n+1)
 
  • #3
Originally posted by martinrandau
Can anybody help me solving this?

Write in terms of factorials

n((n^2)-1)

The correct answer is
(n+1)!/(n-2)!


Please notice the expression marks (!). The task is not to factorise it by "normal" means, but to find an expression as a sequence.
ex. 7! = 1 x 2 x 3 x 4 x 5 x 6 x 7 = 5040
n!= 1 x 2 x 3 x...x n

It's called the factorial r (!).
Thank you for your help anyway!
 
  • #4
Originally posted by martinrandau
The correct answer is
(n+1)!/(n-2)!

I'll give you a hint.

Expand the numerator and denominator of the above ratio and cancel the factors common to both. For instance, the numerator is:

(n+1)!=(n+1)(n)(n-1)(n-2)...

Get the idea?
 
  • #5
Yes!:smile:
Thank you!

//Martin
 

What is a factorial sequence?

A factorial sequence is a sequence of numbers where each number is the product of all the numbers that came before it, including itself. It is represented by the symbol "!" For example, 5! (read as "five factorial") is equal to 5 x 4 x 3 x 2 x 1, which is equal to 120.

How do you calculate the value of a factorial sequence?

To calculate the value of a factorial sequence, you simply multiply all the numbers together in descending order until you reach 1. For example, to calculate 6!, you would multiply 6 x 5 x 4 x 3 x 2 x 1, which equals 720.

What is the difference between factorial and exponential sequences?

The main difference between factorial and exponential sequences is the operation used. Factorial sequences use multiplication, whereas exponential sequences use exponentiation (raising a number to a power). In factorial sequences, the number of terms increases by 1 each time, while in exponential sequences, the power increases by 1 each time.

What is the significance of factorial sequences in mathematics?

Factorial sequences have many applications in mathematics, including in combinatorics, probability, and calculus. They are also used to solve various mathematical problems and are an important concept in understanding the growth of numbers.

Are there any limitations to factorial sequences?

Yes, there are limitations to factorial sequences. One limitation is that the value of a factorial sequence can become very large very quickly, making it difficult to calculate or work with. Additionally, factorial sequences can only be calculated for positive integers, and the sequence becomes undefined for negative numbers or fractions.

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