Question

calculeaza sumele:a)2+4+6+...2018
b)5+10+15+...+2020
c)35+38+41+...+103

urengnt!!!!Dau coroana !am nevoie de asta al 10:00 rapidd

Answer 1

2+4+6+,,,,+2018=2x(1+2+3+,,,,+1009)=2x1009x1010:2=1009x1010=1019090
5+10+15+,,,+2020=5x(1+2+3+,,,+404)=5x404x405:2=2020x405:2=818100:2=409150

Answer 2

a) 2+4+6+...+2018 =
= 2×(1+2+3+...+1009) =
= 2× 1009 × (1009+1) : 2 =
= 1009 × 1010 =
= 1 019 090

b) 5+10+15+...+2020 =
= 5×(1+2+3+...+404) =
= 5×404×(404+1) : 2 =
= 5×202 × 405 =
= 409 050

c) 35+38+41+...+101=
Aflam cati termeni are suma:
(101 - 35) : 3 + 1 = 66:3+1 = 23
= (35+101) × 23 : 2 =
= 136 × 23 : 2 =
= 68 × 23 =
= 1 564

sau
35 + 38 + 41 +...+ 104 =
(104-35):3 + 1 = 69:3+1 = 24 (termeni)
= (35+104) × 24 : 2 =
= 139 × 12 =
= 1 668

la subpunctul c) ai scris gresit ultimul numar al sumei,numarul poate fi (101; 104; 107...) NU 103