高二数学题、、

a1+a3=10

a4+a6=5/4
a1q^3+a3q^3=5/4
q^3(a1+a3)=5/4
q^3=1/8
q=1/2

a1+a3=10
a1+a1q^2=10
5/4a1=10
a1=8

所以a4=a1q^3=8*(1/2)^3=1

S5=a1(1-q^5)/(1-q)=8*(1-(1/2)^5)/(1-1/2)=31/2

设它的公比为q
则a1+a3=a1+a1q^2=a1(1+q^2)=10
a4+a6=a4+a4q^2=a4(1+q^2)=5/4
所以a4/a1=1/8
又a4=a1q^3
所以q^3=1/8解得：q=1/2,a1=8
所以a4=a1q^3=8*(1/2)^3=1
S5=a1(1-q^5)/(1-q)
=8*[1-(1/2)^5]/(1-1/2)
=31/2