1.(1) q>0
a2+a3=24
(1/q+1)a3=24
a4=54=a3*q
得 a3=54/q=24/(1/q+1)
解得 q= -3/4(舍去) 或 q=3
a3=54/q=18
a1=a3/q^2=18/3^2=2
所以a1=2,q=3
(2)S6=a1(1-q^n)/(1-q) =2*(1-3^6)/(1-3)=3^6-1=728
2.(1) a2* q^3=a5,a2=9,a5=243
得,q^3=27
q=3
a1=a2/q=9/3=3
(2)s4=a1(1-q^n)/(1-q) =3*(1-3^4)/(1-3)=3*(1-21)/(-2)=120