Question

calculează sume: a)2+4+6+...+2018
B)5+10+15+...+2020
C)35+38+41+...+103
Plz Dau coroana!!!!

Answer 1

 a)2+4+6+...+2018=2(1+2+3+1009)=2×[(1009×1010]:2=1009×1010=1019090

 B)5+10+15+...+2020=5(1+2+3+...........+404)=5×202×405=409050

 C)35+38+41+...+103

 
103 - 35+1= 69  (numarul de termeni)

S=n×(a1+an)]/2=69×(35+103)]/2=(69×138)/2=4761