Question

cat da cu sirul lui gauss exercitiul: 5+8+11+.....+ 305

Answer 1

5+8+11+..+305=
2+3+2+3*2+2+3*3+....+2+3*101=
2*101+3(1+2+3+...+101)=
202+3*101*102/2=
202+303*51=
202+15453=15655

Answer 2

    
[tex]\displaystyle \text{Calculam numarul de termeni (n) } \\ \\ n= \frac{305 - 5}{3}+1 = \frac{300}{3}+1 = 100+1=101\;termeni \\ \\ S =5+8+11+.....+ 305= \frac{101(305+5)}{2} = \\ \\ =\frac{101\times310}{2} =101\times 155= \boxed{15655} [/tex]