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Cine ma ajuta la.4 $&&$&

Cine Ma Ajuta La4 Ampampamp class=

Răspuns :

(n+1)!/2!(n+1-2)!=15
(n+1)!/2(n-1)!=15
(n-1)!n(n+1)/2(n-1)!=15
n²+n/2=15
n²+n-30=0
∆=1+120=121
n1=-1-11/2=-6 care nu apartine lui N
n2=-1+11/2=5