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# factorial math watch

1. Just need an explanation how does r! * (r+1) =(r+1)! I would have thought it equals (r^2)! +r!

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2. n! = n(n-1)(n-2)(n-3)...3*2*1 right?
let n = r+1

(r+1)! = (r+1)(r)(r-1)(r-2)...3*2*1
= (r+1)[r(r-1)(r-2)...3*2*1]
= (r+1)[r!)

Therefore r!*(r+1) = (r+1)!
3. (Original post by Darth_Narwhale)
n! = n(n-1)(n-2)(n-3)...3*2*1 right?
let n = r+1

(r+1)! = (r+1)(r)(r-1)(r-2)...3*2*1
= (r+1)[r(r-1)(r-2)...3*2*1]
= (r+1)[r!)

Therefore r!*(r+1) = (r+1)!
thanx just worked it out been studying all day brain freez but thanx

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