Question

Va rog ajutati-ma cu exercitiul 1(b,c),ex 3 si ex 4.
Macar un exercitiu va rog.

Answer 1

1) b) {1,2}; {1,3}; [1,4}; {2,3}; {2,4}; {3,4}
c) {1,2,3}; {1,3,4}; {2,3,4}

3) a) n!/(n-2)!=12 => [ (n-2)!(n-1)n ] /(n-2)!=12 => n(n-1)=12
=> n^2-n-12=0.....

b) => 22n!/n!=(n-3)!/(n-4)! => 22=n-3 ...
 
c) 6n!/n!= (n-3)!/(n-5)! => 6=(n-4)(n-3) =>  6=n^2-7n+12 => n^2-7n+6=0....

4) a) => [(n-3)!(n-2)(n-1)] /(n-3)! <=20 =>  (n-2)(n-1)<=20 =>  n^2-3n-18<=0....

b)=>  16n!/5n! >(n-1)!/(n-2)! =>  16/5>n-1....

c) (n-4)!/ [(n-4)!(n-3)(n-2)] >=1/20  =>  1/[ (n-3)(n-2)]>=1/20 =>  (n-3)(n-2) >=20...