Question

Va rog rezolvare completa

Answer 1

Răspuns:

Explicație pas cu pas:

1/2+1/6+1/12+................+1/a(a+1)=2021/2022

1/2=1/1-1/2

1/2·3=1/2-1/3

1/3·4=1/3-1/4

1/a(a+1)=1/a-1/(a+1)

..................................

Suma=1-1/(a+1)=(a+1-1)/(a+1)=a/(a+1)

a/(a+1)=2021/2022   ⇒  2022a=2021(a+1)

2022a=2021a+2021      ⇒a=2021   ⇒raspuns: b