1
q=-3,b1=-6
b5=b1*q^4
b5=-6*(-3)^4=-6*81=-486
2
c1=2,cn+1=-3cn
q=-3
c4=c1*q^3
b5=2*(-3)³=2*(-27)=-54
3
b1=224,b2=336
q=b2/b1
q=336/224=3/2
b5=b1*q^4
b5=224*(3/2)^4=224*81/16b5=1134
4
q=4,b1=1/8
S5=b1*(q^5-1)/(q-1)
S5=1/8*(1024-1):(4-1)=1/8*1023*1/3=341/8=42,625
5
b1=-648,b2=108
q=b2/b1
q=-108/648=
q=-1/6
S5=b1*(1-q^5)/(1-q)
S5=-648*(1+1/7776):(1+1/6)=-648*7777/7776*6/7=-648*1111/1296=-1111/2=-555,5
Ответ -555,5