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Exercitiul 2 va rog frumos

Exercitiul 2 Va Rog Frumos class=

Răspuns :

[tex] \frac{1}{n!}- \frac{1}{(n+2)!}= \frac{1}{n!}-\frac{1}{n!(n+1)(n+2)}= \frac{(n+1)(n+2)-1}{n!(n+1)(n+2)}= \frac{n^2+3n+2-1}{(n+2)!}= [/tex][tex] \frac{n^2+3n+1}{(n+2)!} [/tex]