a4=a1q³
a6=a3q³
所以(a4+a6)/(a1+a3)=q³=(5/4)/10=1/8
q=1/2
a3=a1q²
a1+a3=a1(1+q²)=10
a1=8
a5=a1q^4=1/2
S6=a1(1-q^6)/(1-q)=63/4