Question

se da o progresie geometrica primul termen l1= 2 si ratia q=3 .calculati termenii l2,l5 si S20​

Answer 1

Răspuns:

I(2)=I1 *q=6;

I(5)=2*3^4=162;

S(20)=I(1)+I(2)+...+I(20)=

=2*(1+3+3^2+..+3^19)=

=2*(3^20-1)/(3-1)=3^20-1.