Question

F(2)•F(3)+F(3)•F(4)+...+F(2020)•F(2021)
Va rog Urgent​

Answer 1

Răspuns:

Explicație pas cu pas:

f(2)=1/3   , f(3) = 1/4,  f(4)=1/5,  F(5)=1/6...

S = 1/3*1/4 + 1/4*1/5 + 1/5*1/6+...+1/2020*1/2021=

1/3-1/4 + 1/4-1/5 +1/5-1/6 +...+1/2020-1/2021 =

1/3 - 1/2021 = (2021-3)/(3*2021) =  2018/(3*2021)