Question

Repedee plsss
a1=5 , r=2
a) Calculati primi 6 termeni
b) Calculati a20 si a30

2) Sa se afle termeni de rang
10,15,20 ai progresiei a) -4,-1,2,5,​

Answer 1

1. a) a6= a1+5r= 5+5×2= 5+10=15

S6=(a1+a6)×6/2= (5+15)×3= 20×3=60

b) a20= a6+14r= 60+28= 88

a30= a20+10r= 88+22= 110

2. a1= -4, a2= -1, a3= 2 si a4= 5

r= a2- a1= -1+4= 3

a10= a4+6r= 5+18= 23

a15=a10+5r = 23+15= 38

a20= a15+5r= 38+15= 53