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Ajutor la mate...
Va rog urgent.


Ajutor La Mate Va Rog Urgent class=

Răspuns :

Cn luate cate 2=10⇒
n!/2!(n-2)!=10
n(n-1)(n-2)!/2(n-2)!=10
n(n-1)=20
n²-n-20=0
Δ=b²-4ac=1+80=81
n1=(1-9)/2=-4
n2=(1+9)/2=5
solutia n=5