Ok thanks, I think I understand what you mean,
So 1) n(n-1)=90 then n=10
2) n-2 = 3 then n=5
but if I trie to solve this one it doesn't at up:
3) 2P(n,2)+50=P(2n,2)
2((n!/(n-2))!+50)=2n!/(2n-2)!
Is this correct?
How can I solve this?
Find the value of n.1. P(n,2)=90 ; 2. P(n,3)=3P(n,2)
I tried like this but I am stuck
1. n! / (n-2)! = 90 and then I don't know ...
2. n!/(n-3!) = 3 n!/(n-2)! ⇔ n! (n-2)! / (n-3)! n! = 3 ⇔ (n-2)! / (n-3)! = 3 here the same As you can see I'm really stuck with this.