Q-3, S6-1830 найти b1,b6

Question

Q-3, S6-1830 найти b1,b6

Answer 1

Q=-3;S6=-1830;
S6=b1(1-q⁶)/(1-q);⇒b1=S6(1-q)/(1-q⁶);
b1=-1830(1+3)/(1-729)=-1830·4/(-728)=10.055;
b6=b1·q⁵=10.055·(-243)=-2443.365