Răspuns:
Explicație pas cu pas:
10) B=1-1/2 + 1-1/3 +1-1/4 +...+1-1/2020 =
1*2020 -(1/2 +1/3 +1/4 +...+1/2020)
C = 1/4 +1/4 +1/4 + 1667/668 = (simpl. cu 4 si 6)
3/4 + 1667/668 = (3*167 +1667)/668 =
2168/668 = 542/167 (simpl. cu 4 )
A+B = 1+ (1/2 +1/3 +1/4 +...+1/2020) +1/2021 +
2020 - (1/2 +1/3 +1/4 +...+1/2020)
1 +1/2021 +2020 = 2021 +1/2021
A+B-C = 2021 +1/2021 - 542/167
